Bump puma from 5.6.4 to 5.6.7

Bumps [puma](https://github.com/puma/puma) from 5.6.4 to 5.6.7.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](https://github.com/puma/puma/compare/v5.6.4...v5.6.7)

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

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

Gemfile.lock

@@ -31,8 +31,8 @@ GEM
     multi_xml (0.6.0)
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
-    nio4r (2.5.8)
-    puma (5.6.4)
+    nio4r (2.5.9)
+    puma (5.6.7)
       nio4r (~> 2.0)
     rack (2.2.6.4)
     rack-protection (2.2.0)