Upgrade rust/crates/unicode-segmentation to 1.8.0 am: cdef32ccc4 am: 6cb7f46ab3 am: ab4c798bfc am: 72e8661e14

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/unicode-segmentation/+/1791075

Change-Id: Id35f4fc3c56a8414f984e5d31c904d4aa4d63224