Update rubocop requirement from ~> 0.89 to ~> 1.1

Updates the requirements on [rubocop](https://github.com/rubocop-hq/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v0.89.0...v1.1.0)

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

Author: dependabot-preview[bot]

loofah.gemspec

@@ -39,7 +39,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency("rr", ["~> 1.2.0"])
   spec.add_development_dependency("json", ["~> 2.2"])
   spec.add_development_dependency("concourse", ["~> 0.33"])
-  spec.add_development_dependency("rubocop", ["~> 0.89"])
+  spec.add_development_dependency("rubocop", "~> 1.1")
   spec.add_development_dependency("rdoc", [">= 4.0", "< 7"])
   spec.add_development_dependency("hoe-markdown", ["~> 1.3"])
 end