Add Clang 14 to the build matrix.
Add Clang 14 to the build matrix.

Change-Id: Ica7816a3473512a2d317338c40e1305f4818e498
Reviewed-on: https://code-review.googlesource.com/c/re2/+/59810
Reviewed-by: Justin Lebar <631d11d9fe908fc8f04b5865032c3043cb48fdfb@google.com>
Reviewed-by: Paul Wankadia <62d4e38bb1380f055ec4b899baa75e52af09c5f7@google.com>

google/re2,google/re2,google/re2,google/re2,google/re2