Clean up rust_test_host TEST_MAPPING after default update am: b92a85ff64 am: 15e646d0d5 am: 7321edfbc8 am: 57e5e806f1

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/bencher/+/1582326

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ie7fb60c41e6fea84937c8ede57c690eb6d128324