Upgrade rust/crates/idna to 0.2.1 am: a03885d361 am: 4a80c6526f am: 999b8ffad3 am: 109ec87b1b

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ic62ddbd7db31d0c5b856337009a07a8ac04bd465