Clean up rust_test_host TEST_MAPPING after default update am: 7ef4c8aa23 am: 8c8d5627ec

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/ppv-lite86/+/1584563

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I72f9616cd511b44914e44efeb170cf7f230f2b12