Fixed a typo on the configuration files

Marlin/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/Felix/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/Hephestos/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/Hephestos_2/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/K8200/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/RepRapWorld/Megatronics/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/RigidBot/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/SCARA/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/TAZ4/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/WITBOX/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/adafruit/ST7565/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/delta/biv2.5/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/delta/generic/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/delta/kossel_mini/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/delta/kossel_pro/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/delta/kossel_xl/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/makibox/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //

Marlin/example_configurations/tvrrug/Round2/Configuration.h

 //
 // When enabled Marlin will keep track of some print statistical data such as:
 //  - Total print jobs
-//  - Total successfull print jobs
+//  - Total successful print jobs
 //  - Total failed print jobs
 //  - Total time printing
 //