Bumps [socket2](https://github.com/alexcrichton/socket2-rs) from 0.3.12 to 0.3.15. - [Release notes](https://github.com/alexcrichton/socket2-rs/releases) - [Commits](https://github.com/alexcrichton/socket2-rs/compare/0.3.12...v0.3.15) Signed-off-by: dependabot[bot] <support@github.com>