Bump rack from 2.2.6.2 to 2.2.6.3 in /spec/bundle/insecure_sources (#378)

Bumps [rack](https://github.com/rack/rack) from 2.2.6.2 to 2.2.6.3.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.6.2...v2.2.6.3)

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

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spec/bundle/insecure_sources/Gemfile.lock

@@ -94,7 +94,7 @@ GEM
     nokogiri (1.13.10-x86_64-linux)
       racc (~> 1.4)
     racc (1.6.1)
-    rack (2.2.6.2)
+    rack (2.2.6.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (6.1.3.2)