Remove 'const' from PersistentStore::capacity

Marlin/src/HAL/HAL_AVR/persistent_store_eeprom.cpp

Marlin/src/HAL/HAL_DUE/persistent_store_eeprom.cpp

Marlin/src/HAL/HAL_LPC1768/HAL.cpp

Marlin/src/HAL/HAL_LPC1768/persistent_store_sdcard.cpp

Marlin/src/HAL/HAL_STM32F1/persistent_store_flash.cpp

Marlin/src/HAL/HAL_STM32F1/persistent_store_sdcard.cpp

Marlin/src/HAL/HAL_STM32F4/persistent_store_eeprom.cpp

Marlin/src/HAL/HAL_STM32F7/persistent_store_eeprom.cpp

Marlin/src/HAL/HAL_TEENSY35_36/persistent_store_eeprom.cpp

Marlin/src/HAL/shared/persistent_store_api.h