Clean up rust_test_host TEST_MAPPING after default update am: b8bba2380d

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/bitflags/+/1582230

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I03b08c6ca154cdb84dcad74a5a593cda30dc3618