Update TEST_MAPPING am: 4b1948c7bf

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/async-stream-impl/+/2411813

Change-Id: I78fc5265a7c1f554d47e3bbbd12d3f2cd58a96a8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>