Bump proc-macro2 from 1.0.11 to 1.0.12 (#575)
Bump proc-macro2 from 1.0.11 to 1.0.12 (#575)

Bumps [proc-macro2](https://github.com/alexcrichton/proc-macro2) from 1.0.11 to 1.0.12.
- [Release notes](https://github.com/alexcrichton/proc-macro2/releases)
- [Commits](https://github.com/alexcrichton/proc-macro2/compare/1.0.11...1.0.12)

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

Co-authored-by: dependabot-preview[bot] <6a4c1c4838f800d1998274cd5234e1f65c55e90c@users.noreply.github.com>
alex/ct-tools,alex/ct-tools