Bump puma from 5.6.4 to 5.6.8 (#203)

Bumps [puma](https://github.com/puma/puma) from 5.6.4 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@v5.6.4...v5.6.8)

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

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

Gemfile.lock

@@ -124,7 +124,7 @@ GEM
       ruby2_keywords (~> 0.0.1)
     mustermann-grape (1.0.2)
       mustermann (>= 1.0.0)
-    nio4r (2.5.8)
+    nio4r (2.7.0)
     nokogiri (1.14.3)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
@@ -138,7 +138,7 @@ GEM
       cliver (~> 0.3.1)
       websocket-driver (>= 0.2.0)
     public_suffix (4.0.7)
-    puma (5.6.4)
+    puma (5.6.8)
       nio4r (~> 2.0)
     racc (1.6.2)
     rack (2.2.7)