Remove deprecated SCARA option

Marlin/src/inc/Conditionals_LCD.h

 #define HAS_GAMES     ANY(MARLIN_BRICKOUT, MARLIN_INVADERS, MARLIN_SNAKE, MARLIN_MAZE)
 #define HAS_GAME_MENU (1 < ENABLED(MARLIN_BRICKOUT) + ENABLED(MARLIN_INVADERS) + ENABLED(MARLIN_SNAKE) + ENABLED(MARLIN_MAZE))
 
-#define IS_SCARA     EITHER(MORGAN_SCARA, MAKERARM_SCARA)
+#define IS_SCARA     ENABLED(MORGAN_SCARA)
 #define IS_KINEMATIC (ENABLED(DELTA) || IS_SCARA)
 #define IS_CARTESIAN !IS_KINEMATIC
 

Marlin/src/inc/SanityCheck.h

 #if 1 < 0 \
   + ENABLED(DELTA) \
   + ENABLED(MORGAN_SCARA) \
-  + ENABLED(MAKERARM_SCARA) \
   + ENABLED(COREXY) \
   + ENABLED(COREXZ) \
   + ENABLED(COREYZ) \
   + ENABLED(COREYX) \
   + ENABLED(COREZX) \
   + ENABLED(COREZY)
-  #error "Please enable only one of DELTA, MORGAN_SCARA, MAKERARM_SCARA, COREXY, COREYX, COREXZ, COREZX, COREYZ, or COREZY."
+  #error "Please enable only one of DELTA, MORGAN_SCARA, COREXY, COREYX, COREXZ, COREZX, COREYZ, or COREZY."
 #endif
 
 /**

config/examples/SCARA/Configuration.h

 /**
  * MORGAN_SCARA was developed by QHARLEY in South Africa in 2012-2013.
  * Implemented and slightly reworked by JCERNY in June, 2014.
- *
- * MAKERARM_SCARA is in development, included as an alternate example.
- * Other SCARA models may be added, or SCARA may be unified in the future.
  */
 
 // Specify the specific SCARA model
 #define MORGAN_SCARA
-//#define MAKERARM_SCARA
 
-#if EITHER(MORGAN_SCARA, MAKERARM_SCARA)
+#if ENABLED(MORGAN_SCARA)
 
   //#define DEBUG_SCARA_KINEMATICS
   #define SCARA_FEEDRATE_SCALING // Convert XY feedrate from mm/s to degrees/s on the fly