Bump rubocop-rails from 2.20.2 to 2.21.0

Bumps [rubocop-rails](https://github.com/rubocop/rubocop-rails) from 2.20.2 to 2.21.0.
- [Release notes](https://github.com/rubocop/rubocop-rails/releases)
- [Changelog](https://github.com/rubocop/rubocop-rails/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-rails@v2.20.2...v2.21.0)

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

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

Gemfile.lock

@@ -69,6 +69,7 @@ GEM
       minitest (>= 5.1)
       tzinfo (~> 2.0)
     ast (2.4.2)
+    base64 (0.1.1)
     blueprinter (0.25.3)
     bootsnap (1.16.0)
       msgpack (~> 1.2)
@@ -85,6 +86,7 @@ GEM
       concurrent-ruby (~> 1.0)
     iniparse (1.5.0)
     json (2.6.3)
+    language_server-protocol (3.17.0.3)
     loofah (2.21.3)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -96,7 +98,7 @@ GEM
     marcel (1.0.2)
     method_source (1.0.0)
     mini_mime (1.1.5)
-    minitest (5.19.0)
+    minitest (5.20.0)
     msgpack (1.6.0)
     net-imap (0.3.7)
       date
@@ -159,7 +161,7 @@ GEM
     rainbow (3.1.1)
     rake (13.0.6)
     regexp_parser (2.8.1)
-    rexml (3.2.5)
+    rexml (3.2.6)
     rspec-core (3.12.2)
       rspec-support (~> 3.12.0)
     rspec-expectations (3.12.3)
@@ -177,19 +179,21 @@ GEM
       rspec-mocks (~> 3.12)
       rspec-support (~> 3.12)
     rspec-support (3.12.0)
-    rubocop (1.52.1)
+    rubocop (1.56.2)
+      base64 (~> 0.1.1)
       json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
       parallel (~> 1.10)
       parser (>= 3.2.2.3)
       rainbow (>= 2.2.2, < 4.0)
       regexp_parser (>= 1.8, < 3.0)
       rexml (>= 3.2.5, < 4.0)
-      rubocop-ast (>= 1.28.0, < 2.0)
+      rubocop-ast (>= 1.28.1, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.29.0)
       parser (>= 3.2.1.0)
-    rubocop-rails (2.20.2)
+    rubocop-rails (2.21.0)
       activesupport (>= 4.2.0)
       rack (>= 1.1)
       rubocop (>= 1.33.0, < 2.0)