Fix Ender-2 LCD contrast

Changed the default to overcome the changes in:
5018fdacbe
This commit exposed a bug because the Ender-2 was using a MINIPANEL lcd
and getting default values that were too low, so the text was too weak.
However, the panel should be MKS_MINI_12864, since it
explicitly sets the correct contrast without relying in the defaults.

config/examples/Creality/Ender-2/Configuration.h

 // MakerLab Mini Panel with graphic
 // controller and SD support - http://reprap.org/wiki/Mini_panel
 //
-#define MINIPANEL
+//#define MINIPANEL
 
 //
 // MaKr3d Makr-Panel with graphic controller and SD support.
 // MKS MINI12864 with graphic controller and SD support
 // https://reprap.org/wiki/MKS_MINI_12864
 //
-//#define MKS_MINI_12864
+#define MKS_MINI_12864
 
 //
 // FYSETC variant of the MINI12864 graphic controller with SD support