Clean up rust_test_host TEST_MAPPING after default update am: 0eed533e99

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rustc-hash/+/1585228

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Idfaa795c52a39bd8f75563b500dce62a9d40b4c7