Upgrade rust/crates/regex to 1.4.3 am: 47619ddc40

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/regex/+/1544767

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I5e18bea399d32e11f0769dc2248bc872ac150b58