Update rubocop requirement from ~> 1.12.1 to ~> 1.48.1

Updates the requirements on [rubocop](https://github.com/rubocop/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.12.1...v1.48.1)

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

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

Author: dependabot[bot]

Gemfile

@@ -6,5 +6,5 @@ group :development do
   gem "bundler"
   gem "minitest", "5.18.0"
   gem "coveralls"
-  gem "rubocop", "~> 1.12.1"
+  gem "rubocop", "~> 1.48.1"
 end