Update octokit requirement from ~> 4.0 to >= 4, < 6

Updates the requirements on [octokit](https://github.com/octokit/octokit.rb) to permit the latest version.
- [Release notes](https://github.com/octokit/octokit.rb/releases)
- [Changelog](https://github.com/octokit/octokit.rb/blob/main/RELEASE.md)
- [Commits](octokit/octokit.rb@v4.0.0...v4.22.0)

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

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

Author: dependabot[bot]

github-pages-health-check.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency("addressable", "~> 2.3")
   s.add_dependency("dnsruby", "~> 1.60")
-  s.add_dependency("octokit", "~> 4.0")
+  s.add_dependency("octokit", ">= 4", "< 6")
   s.add_dependency("public_suffix", ">= 3.0", "< 5.0")
   s.add_dependency("typhoeus", "~> 1.3")
 end