Clean up rust_test_host TEST_MAPPING after default update am: 7b41568a63 am: ad02e9381d am: 898fac378d

Original change: https://android-review.googlesource.com/c/platform/external/libchromeos-rs/+/1582586

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ib5b20d0944cb3a99629846be165872f39c2750e6