Update rack requirement from ~> 2.2 to >= 2.2, < 4.0

Updates the requirements on [rack](https://github.com/rack/rack) to permit the latest version.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@2.2.0...3.0.0)

---
updated-dependencies:
- dependency-name: rack
  dependency-type: direct:production
...

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

Author: dependabot[bot]

restful_resource.gemspec

@@ -33,5 +33,5 @@ Gem::Specification.new do |spec|
   spec.add_dependency 'faraday-http-cache', '~> 2.2'
   spec.add_dependency 'faraday_middleware', '~> 1.0'
   spec.add_dependency 'link_header'
-  spec.add_dependency 'rack', '~> 2.2'
+  spec.add_dependency 'rack', '>= 2.2', '< 4.0'
 end