Update rubocop dependency

Gemfile

@@ -18,4 +18,4 @@ group :jekyll_plugins do
 end
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
-gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
+gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]

Gemfile.lock

@@ -3,7 +3,7 @@ GEM
   specs:
     addressable (2.5.1)
       public_suffix (~> 2.0, >= 2.0.2)
-    ast (2.3.0)
+    ast (2.4.0)
     colorator (1.1.0)
     concurrent-ruby (1.0.5)
     execjs (2.7.0)
@@ -53,26 +53,28 @@ GEM
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
     mercenary (0.3.6)
-    parser (2.4.0.0)
-      ast (~> 2.2)
+    parallel (1.12.1)
+    parser (2.5.1.0)
+      ast (~> 2.4.0)
     pathutil (0.14.0)
       forwardable-extended (~> 2.6)
     powerpack (0.1.1)
     public_suffix (2.0.5)
     rack (1.6.8)
-    rainbow (2.2.1)
+    rainbow (3.0.0)
     rake (12.0.0)
     rb-fsevent (0.10.2)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
     rouge (1.11.1)
-    rubocop (0.47.1)
-      parser (>= 2.3.3.1, < 3.0)
+    rubocop (0.56.0)
+      parallel (~> 1.10)
+      parser (>= 2.5)
       powerpack (~> 0.1)
-      rainbow (>= 1.99.1, < 3.0)
+      rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
-    ruby-progressbar (1.8.1)
+    ruby-progressbar (1.9.0)
     rubypants (0.6.0)
     safe_yaml (1.0.4)
     sass (3.4.25)
@@ -81,7 +83,7 @@ GEM
       rack (> 1, < 3)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
-    unicode-display_width (1.3.0)
+    unicode-display_width (1.3.2)
 
 PLATFORMS
   ruby
@@ -99,4 +101,4 @@ DEPENDENCIES
   uglifier
 
 BUNDLED WITH
-   1.14.6
+   1.16.1