Switch these existing variants from `nrf52_base` to `rak4631_hw` (which adds
ENABLE_OTA + the in-place flash store + the EndF post-build hook), so they get
OTA-over-LoRa. Scope is limited to variants already covered by the
Adafruit_nRF52_Bootloader_OTAFIX in-place apply — no new variants are added.
OtaTargets.h is regenerated to include their target ids.