Clean up rust_test_host TEST_MAPPING after default update am: 84fc652c2d

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/unicode-width/+/1584386

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Iec933166c3ae8debdc311b1725dc5ea01cf1a839