Use center defines for Z Safe Homing XY (#17782)

Marlin/Configuration.h

 //#define Z_SAFE_HOMING
 
 #if ENABLED(Z_SAFE_HOMING)
-  #define Z_SAFE_HOMING_X_POINT ((X_BED_SIZE) / 2)    // X point for Z homing when homing all axes (G28).
-  #define Z_SAFE_HOMING_Y_POINT ((Y_BED_SIZE) / 2)    // Y point for Z homing when homing all axes (G28).
+  #define Z_SAFE_HOMING_X_POINT X_CENTER  // X point for Z homing when homing all axes (G28).
+  #define Z_SAFE_HOMING_Y_POINT Y_CENTER  // Y point for Z homing when homing all axes (G28).
 #endif
 
 // Homing speeds (mm/m)