Bump rack from 2.2.9 to 2.2.12 in /examples/simple_rails_api

Bumps [rack](https://github.com/rack/rack) from 2.2.9 to 2.2.12.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.9...v2.2.12)

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

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

Author: dependabot[bot]

examples/simple_rails_api/Gemfile.lock

@@ -106,7 +106,7 @@ GEM
     puma (5.6.9)
       nio4r (~> 2.0)
     racc (1.8.1)
-    rack (2.2.9)
+    rack (2.2.12)
     rack-test (2.1.0)
       rack (>= 1.3)
     rails (6.1.7.8)