build(deps): bump rack in /appengine/rails-hello_world (#1624)

Bumps [rack](https://github.com/rack/rack) from 2.2.10 to 2.2.20.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.10...v2.2.20)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.20
  dependency-type: indirect
...

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

Author: dependabot[bot]

appengine/rails-hello_world/Gemfile.lock

@@ -157,7 +157,7 @@ GEM
     puma (6.4.2)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (2.2.10)
+    rack (2.2.20)
     rack-session (1.0.2)
       rack (< 3)
     rack-test (2.1.0)