Reverts change to force use of 5.10; 5.15 is now available. am: a3441f28a7 am: ce36d15053 am: 804f2ee279 am: 742598945f

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/2113706

Change-Id: Ie2a9a8a28e9ed3cd01332aa06551b260a0166bff
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>