Fix lunch choices for git_main am: acfa31a673

Original change: https://android-review.googlesource.com/c/device/google/bramble/+/2809727

Change-Id: I7df96cb58b73086a543a547e98e8053b2a366666
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>