Make libdowncast_rs product_available am: f4e453af14 am: a2e56ea989 am: a3344ebcfa

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/downcast-rs/+/2441729

Change-Id: I1ee84643d1da1182d20b76b127f44fd14dc865c3
Signed-off-by: Automerger Merge Worker <[email protected]>