Clean up rust_test_host TEST_MAPPING after default update am: 7b41568a63 am: ad02e9381d am: 898fac378d am: cc1a5c8d98

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I61df3c34f411e051710f1e7ca2ef597603e47dc6