Bump rubocop-govuk from 3.3.2 to 3.4.0

Bumps [rubocop-govuk](https://github.com/alphagov/rubocop-govuk) from 3.3.2 to 3.4.0.
- [Release notes](https://github.com/alphagov/rubocop-govuk/releases)
- [Changelog](https://github.com/alphagov/rubocop-govuk/blob/master/CHANGELOG.md)
- [Commits](alphagov/rubocop-govuk@v3.3.2...v3.4.0)

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

Gemfile.lock

@@ -155,7 +155,7 @@ GEM
       mini_portile2 (~> 2.4.0)
     null_logger (0.0.1)
     parallel (1.19.1)
-    parser (2.7.0.5)
+    parser (2.7.1.1)
       ast (~> 2.4.0)
     phantomjs (2.1.1.0)
     plek (3.0.0)
@@ -230,22 +230,25 @@ GEM
       rspec-mocks (~> 3.9)
       rspec-support (~> 3.9)
     rspec-support (3.9.2)
-    rubocop (0.80.1)
+    rubocop (0.81.0)
       jaro_winkler (~> 1.5.1)
       parallel (~> 1.10)
       parser (>= 2.7.0.1)
       rainbow (>= 2.2.2, < 4.0)
       rexml
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 1.4.0, < 1.7)
-    rubocop-govuk (3.3.2)
-      rubocop (= 0.80.1)
+      unicode-display_width (>= 1.4.0, < 2.0)
+    rubocop-govuk (3.4.0)
+      rubocop (= 0.81.0)
       rubocop-rails (~> 2)
+      rubocop-rake (~> 0.5.1)
       rubocop-rspec (~> 1.28)
-    rubocop-rails (2.5.0)
+    rubocop-rails (2.5.2)
       activesupport
       rack (>= 1.1)
       rubocop (>= 0.72.0)
+    rubocop-rake (0.5.1)
+      rubocop
     rubocop-rspec (1.38.1)
       rubocop (>= 0.68.1)
     ruby-progressbar (1.10.1)
@@ -280,14 +283,14 @@ GEM
     thor (0.19.4)
     thread_safe (0.3.6)
     tilt (2.0.10)
-    tzinfo (1.2.6)
+    tzinfo (1.2.7)
       thread_safe (~> 0.1)
     uglifier (4.2.0)
       execjs (>= 0.3.0, < 3)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.6)
-    unicode-display_width (1.6.1)
+    unicode-display_width (1.7.0)
     unicorn (5.5.4)
       kgio (~> 2.6)
       raindrops (~> 0.7)