x15: Update PRODUCT_SHIPPING_API_LEVEL to 31 and FCM to 6 am: 1a3678b99c am: d1ed6a6221

Original change: https://android-review.googlesource.com/c/device/ti/beagle-x15/+/2243382

Change-Id: I6965dba5c505004394e69d6bfe09bc14a9fb4dfe
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>