[Security] Bump websocket-extensions from 0.1.4 to 0.1.5 in /backend

Bumps [websocket-extensions](https://github.com/faye/websocket-extensions-ruby) from 0.1.4 to 0.1.5. **This update includes a security fix.**
- [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-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

backend/Gemfile.lock

@@ -170,7 +170,7 @@ GEM
       railties (>= 6.0.0)
     websocket-driver (0.7.2)
       websocket-extensions (>= 0.1.0)
-    websocket-extensions (0.1.4)
+    websocket-extensions (0.1.5)
     xpath (3.2.0)
       nokogiri (~> 1.8)
     zeitwerk (2.3.0)