Fix Photograph Pin Sanity Check (#15406)

Marlin/src/inc/SanityCheck.h

  * Photo G-code requirements
  */
 #if ENABLED(PHOTO_GCODE)
-  #if (PIN_EXISTS(CHDK) + PIN_EXISTS(PHOTOGRAPH_PIN) + defined(PHOTO_SWITCH_POSITION)) > 1
+  #if (PIN_EXISTS(CHDK) + PIN_EXISTS(PHOTOGRAPH) + defined(PHOTO_SWITCH_POSITION)) > 1
     #error "Please define only one of CHDK_PIN, PHOTOGRAPH_PIN, or PHOTO_SWITCH_POSITION."
   #elif defined(PHOTO_SWITCH_POSITION) && !defined(PHOTO_POSITION)
     #error "PHOTO_SWITCH_POSITION requires PHOTO_POSITION. Please update your Configuration_adv.h."