Update Unicode data to 15.0.0.

Change-Id: I73650fd2844d4a892275b4234cfde343152e415a
Reviewed-on: https://code-review.googlesource.com/c/re2/+/60470
Reviewed-by: Paul Wankadia <junyer@google.com>
Reviewed-by: Perry Lorier <perryl@google.com>
4 files changed