chore(deps): bump puma in /buildpacks/buildpack-ruby/tests/ruby-sinatra

Bumps [puma](https://github.com/puma/puma) from 6.4.2 to 6.4.3.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v6.4.2...v6.4.3)

---
updated-dependencies:
- dependency-name: puma
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

buildpacks/buildpack-ruby/tests/ruby-sinatra/Gemfile.lock

@@ -4,9 +4,9 @@ GEM
     base64 (0.2.0)
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
-    nio4r (2.7.0)
+    nio4r (2.7.3)
     power_assert (2.0.3)
-    puma (6.4.2)
+    puma (6.4.3)
       nio4r (~> 2.0)
     rack (3.1.7)
     rack-protection (4.0.0)