Bump rack from 2.2.13 to 2.2.15

Bumps [rack](https://github.com/rack/rack) from 2.2.13 to 2.2.15.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.13...v2.2.15)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.15
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -139,7 +139,7 @@ GEM
       mojo_magick (~> 0.6.5)
       rqrcode_core (~> 1.0)
     racc (1.8.1)
-    rack (2.2.13)
+    rack (2.2.15)
     rack-protection (3.2.0)
       base64 (>= 0.1.0)
       rack (~> 2.2, >= 2.2.4)