Merge "Upgrade regex-syntax to 0.6.28" am: aa41e2c8d7 am: a6de87ad58 am: d501dae5ec

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/regex-syntax/+/2349095

Change-Id: Ibf08bf3890444194706a0359b8798536366fdf39
Signed-off-by: Automerger Merge Worker <[email protected]>