Clean up some boot screens

Marlin/src/config/examples/Formbot/T_Rex_2+/_Bootscreen.h

 #include <avr/pgmspace.h>
 
 #define CUSTOM_BOOTSCREEN_TIMEOUT   2500
-
 #define CUSTOM_BOOTSCREEN_BMPWIDTH  128
-#define CUSTOM_BOOTSCREEN_BMPHEIGHT 64
 
 const unsigned char custom_start_bmp[] PROGMEM = {
   B11110000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00001111,

Marlin/src/config/examples/Formbot/T_Rex_3/_Bootscreen.h

 #include <avr/pgmspace.h>
 
 #define CUSTOM_BOOTSCREEN_TIMEOUT   2500
-
 #define CUSTOM_BOOTSCREEN_BMPWIDTH  128
-#define CUSTOM_BOOTSCREEN_BMPHEIGHT 64
 
 const unsigned char custom_start_bmp[] PROGMEM = {
   B11110000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00000000,B00001111,