Fix typo (# missing before define).

Marlin/Configuration.h

 #define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)
 
 // The position of the homing switches
-define MANUAL_HOME_POSITIONS  // If defined, MANUAL_*_HOME_POS below will be used
+#define MANUAL_HOME_POSITIONS  // If defined, MANUAL_*_HOME_POS below will be used
 //#define BED_CENTER_AT_0_0  // If defined, the center of the bed is at (X=0, Y=0)
 
 // Manual homing switch locations: