Add prebuilt protobuf 3.9.1 to vendor partition. am: f180675fc4

Original change: https://android-review.googlesource.com/c/device/google/redfin/+/2299060

Change-Id: I22f152496d6e2a5ac937ff64d9a9b23c45d35659
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>