Bump rubocop from 1.8.0 to 1.8.1

Bumps [rubocop](https://github.com/rubocop-hq/rubocop) from 1.8.0 to 1.8.1.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.8.0...v1.8.1)

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

Gemfile.lock

@@ -33,7 +33,7 @@ GEM
     rake (13.0.3)
     regexp_parser (2.0.3)
     rexml (3.2.4)
-    rubocop (1.8.0)
+    rubocop (1.8.1)
       parallel (~> 1.10)
       parser (>= 3.0.0.0)
       rainbow (>= 2.2.2, < 4.0)