Bump websocket-extensions from 0.1.4 to 0.1.5 in /back-end

Bumps [websocket-extensions](https://github.com/faye/websocket-extensions-ruby) from 0.1.4 to 0.1.5.
- [Release notes](https://github.com/faye/websocket-extensions-ruby/releases)
- [Changelog](https://github.com/faye/websocket-extensions-ruby/blob/master/CHANGELOG.md)
- [Commits](faye/websocket-extensions-ruby@0.1.4...0.1.5)

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

Author: dependabot[bot]

back-end/Gemfile.lock

@@ -130,7 +130,7 @@ GEM
       thread_safe (~> 0.1)
     websocket-driver (0.7.1)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.4)
+    websocket-extensions (0.1.5)
 
 PLATFORMS
   ruby