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

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ib96391874112990f0825da63b0bd20b37bb6f8cf