Update TEST_MAPPING am: 51b265d07a

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/codespan-reporting/+/2107313

Change-Id: Ie0e6615dada0d18f226ec06810f0a4bcfa5f45c6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>