Copy description from Cargo.toml to METADATA am: 0e60726f90 am: 4c2fb019b8 am: 736efd0f99 am: 9becc05454

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/smallvec/+/1456780

Change-Id: I9e25928d62170036bcb557f66be6052fd8312ef0