Bump rubocop from 1.30.1 to 1.31.1

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.30.1 to 1.31.1.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.30.1...v1.31.1)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -153,6 +153,7 @@ GEM
       gemoji (~> 3.0)
       html-pipeline (~> 2.2)
       jekyll (>= 3.0, < 5.0)
+    json (2.6.2)
     kramdown (2.4.0)
       rexml
     kramdown-parser-gfm (1.1.0)
@@ -214,7 +215,8 @@ GEM
     regexp_parser (2.5.0)
     rexml (3.2.5)
     rouge (3.29.0)
-    rubocop (1.30.1)
+    rubocop (1.31.1)
+      json (~> 2.3)
       parallel (~> 1.10)
       parser (>= 3.1.0.0)
       rainbow (>= 2.2.2, < 4.0)