Bump puma from 5.6.7 to 5.6.8

Bumps [puma](https://github.com/puma/puma) from 5.6.7 to 5.6.8.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v5.6.7...v5.6.8)

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

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

Gemfile.lock

@@ -16,15 +16,15 @@ GEM
     multipart-post (2.0.0)
     mustermann (2.0.2)
       ruby2_keywords (~> 0.0.1)
-    nio4r (2.5.9)
+    nio4r (2.7.1)
     panoptes-client (0.3.8)
       faraday
       faraday-panoptes (~> 0.3.0)
       jwt (~> 1.5.0)
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    puma (5.6.7)
+    puma (5.6.8)
       nio4r (~> 2.0)
     rack (2.2.6.4)
     rack-protection (2.2.3)