Bump rack from 2.2.4 to 2.2.6.4 (#986)

Bumps [rack](https://github.com/rack/rack) from 2.2.4 to 2.2.6.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](https://github.com/rack/rack/compare/2.2.4...v2.2.6.4)

---
updated-dependencies:
- dependency-name: rack
  dependency-type: indirect
...

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Gemfile.lock

@@ -326,7 +326,7 @@ GEM
     puma (5.6.5)
       nio4r (~> 2.0)
     racc (1.6.1)
-    rack (2.2.4)
+    rack (2.2.6.4)
     rack-contrib (2.3.0)
       rack (~> 2.0)
     rack-cors (1.1.1)