Update simplecov requirement from ~> 0.21.0 to ~> 0.22.0

Updates the requirements on [simplecov](https://github.com/simplecov-ruby/simplecov) to permit the latest version.
- [Release notes](https://github.com/simplecov-ruby/simplecov/releases)
- [Changelog](https://github.com/simplecov-ruby/simplecov/blob/main/CHANGELOG.md)
- [Commits](https://github.com/simplecov-ruby/simplecov/compare/v0.21.0...v0.22.0)

---
updated-dependencies:
- dependency-name: simplecov
  dependency-type: direct:development
...

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

wpscan.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec-its',           '~> 1.3.0'
   s.add_development_dependency 'rubocop',             '~> 1.26.0'
   s.add_development_dependency 'rubocop-performance', '~> 1.13.0'
-  s.add_development_dependency 'simplecov',           '~> 0.21.0'
+  s.add_development_dependency 'simplecov',           '~> 0.22.0'
   s.add_development_dependency 'simplecov-lcov',      '~> 0.8.0'
   s.add_development_dependency 'stackprof',           '~> 0.2.12'
   s.add_development_dependency 'webmock',             '~> 3.18.1'