Clean up rust_test_host TEST_MAPPING after default update am: ab7dbba14c am: 1e83984d27

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/proc-macro-error-attr/+/1584352

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I2cc7b46fab3a0a713e3cab34e861daadc631cff9