Update Jekyll with security patch (jekyll/jekyll#7224)

docs/Gemfile

@@ -8,7 +8,7 @@ source "https://rubygems.org"
 #
 # This will help ensure the proper Jekyll version is running.
 # Happy Jekylling!
-gem "jekyll", "~> 3.7.3"
+gem "jekyll", "~> 3.7.4"
 
 # This is the default theme for new Jekyll sites. You may change this to anything you like.
 # gem "minima", "~> 2.0"

docs/Gemfile.lock

@@ -8,13 +8,13 @@ GEM
     em-websocket (0.5.1)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
-    eventmachine (1.2.5)
-    ffi (1.9.23)
+    eventmachine (1.2.7)
+    ffi (1.9.25)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
-    jekyll (3.7.3)
+    jekyll (3.7.4)
       addressable (~> 2.4)
       colorator (~> 1.0)
       em-websocket (~> 0.5)
@@ -27,29 +27,29 @@ GEM
       pathutil (~> 0.9)
       rouge (>= 1.7, < 4)
       safe_yaml (~> 1.0)
-    jekyll-feed (0.9.3)
+    jekyll-feed (0.11.0)
       jekyll (~> 3.3)
     jekyll-sass-converter (1.5.2)
       sass (~> 3.4)
     jekyll-watch (2.0.0)
       listen (~> 3.0)
-    kramdown (1.16.2)
-    liquid (4.0.0)
+    kramdown (1.17.0)
+    liquid (4.0.1)
     listen (3.1.5)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
     mercenary (0.3.6)
     pathutil (0.16.1)
       forwardable-extended (~> 2.6)
-    public_suffix (3.0.2)
-    rb-fsevent (0.10.2)
+    public_suffix (3.0.3)
+    rb-fsevent (0.10.3)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    rouge (3.1.1)
+    rouge (3.3.0)
     ruby_dep (1.5.0)
     safe_yaml (1.0.4)
-    sass (3.5.5)
+    sass (3.6.0)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
@@ -59,7 +59,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  jekyll (~> 3.7.3)
+  jekyll (~> 3.7.4)
   jekyll-feed (~> 0.6)
   tzinfo-data