Bump concurrent-ruby from 1.1.8 to 1.1.9

Bumps [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby) from 1.1.8 to 1.1.9.
- [Release notes](https://github.com/ruby-concurrency/concurrent-ruby/releases)
- [Changelog](https://github.com/ruby-concurrency/concurrent-ruby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ruby-concurrency/concurrent-ruby/compare/v1.1.8...v1.1.9)

---
updated-dependencies:
- dependency-name: concurrent-ruby
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -138,7 +138,7 @@ GEM
     childprocess (3.0.0)
     chronic (0.10.2)
     coderay (1.1.3)
-    concurrent-ruby (1.1.8)
+    concurrent-ruby (1.1.9)
     crack (0.4.5)
       rexml
     crass (1.0.6)