chore: bump puma in /integration/examples/ruby/backend (GoogleContain…

…erTools#9528)

Bumps [puma](https://github.com/puma/puma) from 5.6.8 to 5.6.9.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v5.6.8...v5.6.9)

---
updated-dependencies:
- dependency-name: puma
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

integration/examples/ruby/backend/Gemfile.lock

@@ -1,8 +1,8 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    nio4r (2.7.0)
-    puma (5.6.8)
+    nio4r (2.7.3)
+    puma (5.6.9)
       nio4r (~> 2.0)
     rack (2.2.8.1)
     rack-unreloader (1.7.0)