Bump concurrent-ruby from 1.3.6 to 1.3.7

Bumps [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby) from 1.3.6 to 1.3.7.
- [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@v1.3.6...v1.3.7)

---
updated-dependencies:
- dependency-name: concurrent-ruby
  dependency-version: 1.3.7
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -71,7 +71,7 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    concurrent-ruby (1.3.6)
+    concurrent-ruby (1.3.7)
     connection_pool (3.0.2)
     contracts (0.17.3)
     cuprite (0.17)