chore(deps): bump thin from 1.8.0 to 1.8.1 in /tests/apps/ruby

Bumps [thin](https://github.com/macournoyer/thin) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/macournoyer/thin/releases)
- [Changelog](https://github.com/macournoyer/thin/blob/master/CHANGELOG)
- [Commits](https://github.com/macournoyer/thin/compare/v1.8.0...v1.8.1)

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

tests/apps/ruby/Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    daemons (1.3.1)
+    daemons (1.4.0)
     eventmachine (1.2.7)
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
@@ -14,7 +14,7 @@ GEM
       rack (~> 2.2)
       rack-protection (= 2.1.0)
       tilt (~> 2.0)
-    thin (1.8.0)
+    thin (1.8.1)
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)