Bump concurrent-ruby from 1.3.5 to 1.3.7 in /example

Bumps [concurrent-ruby](https://github.com/ruby-concurrency/concurrent-ruby) from 1.3.5 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@v1.3.5...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]

example/Gemfile.lock

@@ -63,7 +63,7 @@ GEM
       netrc (~> 0.11)
     cocoapods-try (1.2.0)
     colored2 (3.1.2)
-    concurrent-ruby (1.3.5)
+    concurrent-ruby (1.3.7)
     connection_pool (2.5.5)
     drb (2.2.3)
     escape (0.0.4)