Bump rack from 2.2.14 to 2.2.18 (#9)

Bumps [rack](https://github.com/rack/rack) from 2.2.14 to 2.2.18.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.14...v2.2.18)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.18
  dependency-type: indirect
...

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Author: dependabot[bot]

Gemfile.lock

@@ -25,7 +25,7 @@ GEM
       multi_json (~> 1.3)
       multi_xml (~> 0.5)
       rack (>= 1.2, < 3)
-    rack (2.2.14)
+    rack (2.2.18)
     ruby2_keywords (0.0.4)
 
 PLATFORMS