Clean up rust_test_host TEST_MAPPING after default update am: ba5a029d7f am: 2707f6726c

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/futures-macro/+/1590491

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I5f680960e076e3f27d72b7a34bca9fcab2dcb63a