build(deps): bump rack from 2.2.19 to 2.2.20 in /docs/v3 (#4603)

Bumps [rack](https://github.com/rack/rack) from 2.2.19 to 2.2.20.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.19...v2.2.20)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.20
  dependency-type: indirect
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/v3/Gemfile.lock

@@ -118,7 +118,7 @@ GEM
     parslet (2.0.0)
     public_suffix (5.0.5)
     racc (1.8.1)
-    rack (2.2.19)
+    rack (2.2.20)
     rack-livereload (0.3.17)
       rack
     rake (13.3.0)