Update rubocop-rspec requirement from ~> 2.29 to ~> 3.0

Updates the requirements on [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rspec@v2.29.0...v3.0.1)

---
updated-dependencies:
- dependency-name: rubocop-rspec
  dependency-type: direct:production
...

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

gemfiles/rubocop.gemfile

@@ -4,5 +4,5 @@ source "https://rubygems.org" do
   gem "standard", "~> 1.35"
   gem "rubocop-md", "~> 1.2"
   gem "rubocop-rake", "~> 0.6"
-  gem "rubocop-rspec", "~> 2.29"
+  gem "rubocop-rspec", "~> 3.0"
 end