Bump govuk_tech_docs to 2.4.2

Brings in a bunch of accessibility fixes:

https://github.com/alphagov/tech-docs-gem/blob/master/CHANGELOG.md#240

(And a few patches for bugs found along the way.)

This also bumps the ffi gem which caused this
issue:

ffi/ffi#791

The fix at the moment is just to keep ffi at
1.12 until the issue is resolved so this also adds
that to the Gemfile.

There is an issue on govuk_tech_docs to pin ffi
there instead of downstream apps so we should
revert our pin if this happens:

alphagov/tech-docs-gem#254

Gemfile

@@ -2,9 +2,13 @@ source 'https://rubygems.org'
 
 gem 'faraday', '~> 1.0.0'
 gem 'govuk-lint', '~> 4.0.1'
-gem 'govuk_tech_docs', '~> 2.2.2'
+gem 'govuk_tech_docs', '~> 2.4.2'
 gem 'mini_racer', '~> 0.3.1'
 
+# Include specific version of FFI until following issue is fixed:
+# https://github.com/ffi/ffi/issues/791
+gem "ffi", "1.12"
+
 group :test do
   gem 'rspec', '~> 3.9.0'
   gem 'webmock', '~> 3.8.2'

Gemfile.lock

@@ -1,25 +1,24 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (5.2.4.5)
+    activesupport (5.2.6)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
     addressable (2.8.0)
       public_suffix (>= 2.0.2, < 5.0)
     ast (2.4.0)
-    autoprefixer-rails (9.8.6.5)
-      execjs
-    backports (3.20.2)
+    autoprefixer-rails (10.2.5.1)
+      execjs (> 0)
+    backports (3.21.0)
     chronic (0.10.2)
     chunky_png (1.4.0)
     coffee-script (2.4.1)
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    commonmarker (0.21.2)
-      ruby-enum (~> 0.5)
+    commonmarker (0.22.0)
     compass (1.0.3)
       chunky_png (~> 1.2)
       compass-core (~> 1.0.2)
@@ -32,7 +31,7 @@ GEM
       sass (>= 3.3.0, < 3.5)
     compass-import-once (1.0.5)
       sass (>= 3.2, < 3.5)
-    concurrent-ruby (1.1.8)
+    concurrent-ruby (1.1.9)
     contracts (0.13.0)
     crack (0.4.3)
       safe_yaml (~> 1.0.0)
@@ -43,18 +42,19 @@ GEM
       http_parser.rb (~> 0.6.0)
     erubis (2.7.0)
     eventmachine (1.2.7)
-    execjs (2.7.0)
+    execjs (2.8.1)
     faraday (1.0.0)
       multipart-post (>= 1.2, < 3)
     fast_blank (1.0.0)
-    fastimage (2.2.3)
-    ffi (1.15.0)
+    fastimage (2.2.4)
+    ffi (1.12.0)
     govuk-lint (4.0.1)
       rubocop (~> 0.72)
       rubocop-rails (~> 2)
       rubocop-rspec (~> 1.28)
       scss_lint
-    govuk_tech_docs (2.2.2)
+    govuk_tech_docs (2.4.2)
+      autoprefixer-rails (~> 10.2)
       chronic (~> 0.10.2)
       middleman (~> 4.0)
       middleman-autoprefixer (~> 2.10.0)
@@ -65,8 +65,8 @@ GEM
       middleman-syntax (~> 3.2.0)
       nokogiri
       openapi3_parser (~> 0.9.0)
-      redcarpet (~> 3.5.0)
-    haml (5.2.1)
+      redcarpet (~> 3.5.1)
+    haml (5.2.2)
       temple (>= 0.8.0)
       tilt
     hamster (3.0.0)
@@ -90,8 +90,8 @@ GEM
       kramdown (>= 2.3.0)
       middleman-cli (= 4.3.11)
       middleman-core (= 4.3.11)
-    middleman-autoprefixer (2.10.1)
-      autoprefixer-rails (~> 9.1)
+    middleman-autoprefixer (2.10.0)
+      autoprefixer-rails (>= 9.1.4)
       middleman-core (>= 3.3.3)
     middleman-cli (4.3.11)
       thor (>= 0.17.0, < 2.0)
@@ -121,7 +121,7 @@ GEM
       servolux
       tilt (~> 2.0.9)
       uglifier (~> 3.0)
-    middleman-livereload (3.4.6)
+    middleman-livereload (3.4.7)
       em-websocket (~> 0.5.1)
       middleman-core (>= 3.3)
       rack-livereload (~> 0.3.15)
@@ -135,13 +135,13 @@ GEM
     middleman-syntax (3.2.0)
       middleman-core (>= 3.2)
       rouge (~> 3.2)
-    mini_portile2 (2.5.1)
+    mini_portile2 (2.5.3)
     mini_racer (0.3.1)
       libv8 (~> 8.4.255)
     minitest (5.14.4)
     multi_json (1.15.0)
     multipart-post (2.1.1)
-    nokogiri (1.11.4)
+    nokogiri (1.11.7)
       mini_portile2 (~> 2.5.0)
       racc (~> 1.4)
     openapi3_parser (0.9.0)
@@ -156,15 +156,15 @@ GEM
     parallel (1.19.1)
     parser (2.6.5.0)
       ast (~> 2.4.0)
-    psych (3.3.1)
+    psych (3.3.2)
     public_suffix (4.0.6)
     racc (1.5.2)
     rack (2.2.3)
     rack-livereload (0.3.17)
       rack
     rainbow (3.0.0)
     rake (12.3.3)
-    rb-fsevent (0.10.4)
+    rb-fsevent (0.11.0)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
     redcarpet (3.5.1)
@@ -195,8 +195,6 @@ GEM
       rubocop (>= 0.72.0)
     rubocop-rspec (1.36.0)
       rubocop (>= 0.68.1)
-    ruby-enum (0.9.0)
-      i18n
     ruby-progressbar (1.10.1)
     safe_yaml (1.0.5)
     sass (3.4.25)
@@ -228,8 +226,9 @@ PLATFORMS
 
 DEPENDENCIES
   faraday (~> 1.0.0)
+  ffi (= 1.12)
   govuk-lint (~> 4.0.1)
-  govuk_tech_docs (~> 2.2.2)
+  govuk_tech_docs (~> 2.4.2)
   mini_racer (~> 0.3.1)
   rspec (~> 3.9.0)
   webmock (~> 3.8.2)