Update parallel_tests requirement from = 3.12.1 to 3.13.0

Updates the requirements on [parallel_tests](https://github.com/grosser/parallel_tests) to permit the latest version.
- [Changelog](https://github.com/grosser/parallel_tests/blob/master/CHANGELOG.md)
- [Commits](https://github.com/grosser/parallel_tests/commits)

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

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

Author: dependabot[bot]

Gemfile

@@ -26,7 +26,7 @@ group :development do
   gem "metadata-json-lint", '~> 4.0',            require: false
   gem "rspec-puppet-facts", '~> 3.0',            require: false
   gem "dependency_checker", '~> 1.0.0',          require: false
-  gem "parallel_tests", '= 3.12.1',              require: false
+  gem "parallel_tests", '3.13.0',              require: false
   gem "pry", '~> 0.10',                          require: false
   gem "simplecov-console", '~> 0.9',             require: false
   gem "puppet-debugger", '~> 1.0',               require: false