Bump regex-syntax from 0.6.20 to 0.6.21
Bump regex-syntax from 0.6.20 to 0.6.21

Bumps [regex-syntax](https://github.com/rust-lang/regex) from 0.6.20 to 0.6.21.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/regex/commits)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
ryanfowler/lines