build(deps): bump rack (#1389)

Bumps [rack](https://github.com/rack/rack) from 2.2.8 to 2.2.8.1.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.8...v2.2.8.1)

---
updated-dependencies:
- dependency-name: rack
  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/flexible/ruby31-and-earlier/rails-cloudsql-postgres/Gemfile.lock

@@ -186,7 +186,7 @@ GEM
     public_suffix (5.0.3)
     puma (3.12.6)
     racc (1.7.3)
-    rack (2.2.8)
+    rack (2.2.8.1)
     rack-test (2.1.0)
       rack (>= 1.3)
     rails (5.2.8.1)