Bump rack from 2.2.6.3 to 2.2.6.4

Bumps [rack](https://github.com/rack/rack) from 2.2.6.3 to 2.2.6.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.6.3...v2.2.6.4)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -150,7 +150,7 @@ GEM
       method_source (~> 1.0)
     public_suffix (4.0.6)
     racc (1.6.1)
-    rack (2.2.6.3)
+    rack (2.2.6.4)
     rack-livereload (0.3.17)
       rack
     rake (13.0.1)