samples: boards: fix bbc_microbit pong build
samples: boards: fix bbc_microbit pong build

The GATT caching feature isn't needed, and was making the memory
consumption blow up because of the recent addition of `long_wq` for
deferred work.

Fixes #47428 .

Signed-off-by: Jonathan Rico <fa71e224653c2b3d230eecbd20dc417397790bdf@nordicsemi.no>

galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr