Bump websocket-extensions from 0.1.2 to 0.1.5

Bumps [websocket-extensions](https://github.com/faye/websocket-extensions-ruby) from 0.1.2 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](https://github.com/faye/websocket-extensions-ruby/compare/0.1.2...0.1.5)

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

Gemfile.lock

@@ -123,7 +123,7 @@ GEM
       addressable
     websocket-driver (0.7.0)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.2)
+    websocket-extensions (0.1.5)
     xpath (2.1.0)
       nokogiri (~> 1.3)