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: I76bc525e3e30dd83fa65b95e83a644e880ebe805
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>