Bump puma from 5.6.4 to 5.6.8

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:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -136,7 +136,7 @@ GEM
     mini_portile2 (2.8.0)
     minitest (5.14.4)
     msgpack (1.6.0)
-    nio4r (2.5.8)
+    nio4r (2.7.0)
     nokogiri (1.13.10)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
@@ -149,7 +149,7 @@ GEM
       coderay (~> 1.1)
       method_source (~> 1.0)
     public_suffix (4.0.6)
-    puma (5.6.4)
+    puma (5.6.8)
       nio4r (~> 2.0)
     racc (1.6.1)
     rack (2.2.6.4)