Upgrade rust/crates/idna to 0.2.1 am: a03885d361 am: 4a80c6526f

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/idna/+/1581958

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ie78fc381901ffbb79c3524b100617878a3c91e33