Delete the `AUTHORS` and `CONTRIBUTORS` files.

I discovered from https://github.com/golang/go/issues/53961 and
elsewhere that our lawyercats no longer require these files for
licensing compliance. Which is just as well because these files
haven't been touched since 2014...

Change-Id: I7f4cabeae86b08703ad7f145e5354e78b6baa59f
Reviewed-on: https://code-review.googlesource.com/c/re2/+/62310
Reviewed-by: Paul Wankadia <junyer@google.com>
Reviewed-by: Alex Chernyakhovsky <achernya@google.com>
2 files changed