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](ruby-concurrency/concurrent-ruby@v1.1.8...v1.1.9)

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

Gemfile.lock

@@ -22,7 +22,7 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    concurrent-ruby (1.1.8)
+    concurrent-ruby (1.1.9)
     contracts (0.13.0)
     dotenv (2.7.5)
     em-websocket (0.5.1)