Bump concurrent-ruby from 1.1.10 to 1.2.3 in /.overcommit

Bumps [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby) from 1.1.10 to 1.2.3.
- [Release notes](https://github.com/ruby-concurrency/concurrent-ruby/releases)
- [Changelog](https://github.com/ruby-concurrency/concurrent-ruby/blob/master/CHANGELOG.md)
- [Commits](ruby-concurrency/concurrent-ruby@v1.1.10...v1.2.3)

---
updated-dependencies:
- dependency-name: concurrent-ruby
  dependency-type: indirect
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

.overcommit/Gemfile.lock

@@ -22,7 +22,7 @@ GEM
     ast (2.4.2)
     brakeman (5.2.3)
     childprocess (4.1.0)
-    concurrent-ruby (1.1.10)
+    concurrent-ruby (1.2.3)
     i18n (1.10.0)
       concurrent-ruby (~> 1.0)
     iniparse (1.5.0)