Clean up rust_test_host TEST_MAPPING after default update am: 12f47a0789

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/pin-project-internal/+/1590752

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ife4b986b5500d97457893e8583cbdd6e72b63a91