build(deps): bump rack in /appengine/standard-static-files/sinatra (#1377)

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/standard-static-files/sinatra/Gemfile.lock

@@ -35,7 +35,7 @@ GEM
     puma (6.4.2)
       nio4r (~> 2.0)
     racc (1.7.3)
-    rack (2.2.8)
+    rack (2.2.8.1)
     rack-protection (3.1.0)
       rack (~> 2.2, >= 2.2.4)
     rack-test (2.1.0)