Update rubocop requirement from ~> 0.91.0 to ~> 0.92.0

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@v0.91.0...v0.92.0)

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

Author: dependabot-preview[bot]

activerecord-safer_migrations.gemspec

@@ -20,5 +20,5 @@ Gem::Specification.new do |gem|
 
   gem.add_development_dependency "pg", "~> 1.2.3"
   gem.add_development_dependency "rspec", "~> 3.9.0"
-  gem.add_development_dependency "rubocop", "~> 0.91.0"
+  gem.add_development_dependency "rubocop", "~> 0.92.0"
 end