✏️ Fix a label (#24903)

Followup to e298266eff

Marlin/src/HAL/STM32/eeprom_flash.cpp

 
       return success;
 
-    #else !FLASH_EEPROM_LEVELING
+    #else // !FLASH_EEPROM_LEVELING
 
       // The following was written for the STM32F4 but may work with other MCUs as well.
       // Most STM32F4 flash does not allow reading from flash during erase operations.