Clean up rust_test_host TEST_MAPPING after default update am: b92a85ff64 am: 15e646d0d5

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I7f0beb66d9012375987f4c21293c3514e74da333