Upgrade regex to 1.7.3 am: 1380782414 am: 65db4c2575 am: a412b776b1 am: c2d558aa13 am: 240bf05ef7

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/regex/+/2519976

Change-Id: I07a20d4a9cafcbad43d7445c7463c72fdfc3bb21
Signed-off-by: Automerger Merge Worker <[email protected]>