Upgrade tech-docs-gem to v4.1.2

Brings in the following accessibility fixes:
- making focus return to the table of contents
  button when its dialog closes
- stop the main content pane being focusable on
  mobile or at high zoom levels
- give the main content pane a focus style on
  desktop or at the default zoom level

See alphagov/tech-docs-gem#381

Author: tombye

Gemfile

@@ -1,4 +1,4 @@
 source 'https://rubygems.org'
 
-gem 'govuk_tech_docs', '~> 4.1.1'
+gem 'govuk_tech_docs', '~> 4.1.2'
 gem 'mini_racer', '~> 0.8.0'

Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (7.0.8.6)
+    activesupport (7.0.8.7)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
@@ -12,14 +12,14 @@ GEM
       execjs (~> 2)
     backports (3.25.0)
     base64 (0.2.0)
-    bigdecimal (3.1.8)
+    bigdecimal (3.1.9)
     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 (0.23.10)
+    commonmarker (0.23.11)
     compass (1.0.3)
       chunky_png (~> 1.2)
       compass-core (~> 1.0.2)
@@ -34,29 +34,30 @@ GEM
       sass (>= 3.2, < 3.5)
     concurrent-ruby (1.3.4)
     contracts (0.16.1)
-    csv (3.3.0)
-    dotenv (3.1.4)
+    csv (3.3.2)
+    dotenv (3.1.7)
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
     erubis (2.7.0)
     eventmachine (1.2.7)
     execjs (2.10.0)
     fast_blank (1.0.1)
-    fastimage (2.3.1)
-    ffi (1.17.0-aarch64-linux-gnu)
-    ffi (1.17.0-arm64-darwin)
-    google-protobuf (4.28.3-aarch64-linux)
+    fastimage (2.4.0)
+    ffi (1.17.1-aarch64-linux-gnu)
+    ffi (1.17.1-arm64-darwin)
+    google-protobuf (4.29.3-aarch64-linux)
       bigdecimal
       rake (>= 13)
-    google-protobuf (4.28.3-arm64-darwin)
+    google-protobuf (4.29.3-arm64-darwin)
       bigdecimal
       rake (>= 13)
-    govuk_tech_docs (4.1.1)
+    govuk_tech_docs (4.1.2)
       autoprefixer-rails (~> 10.2)
       base64
       bigdecimal
       chronic (~> 0.10.2)
+      concurrent-ruby (= 1.3.4)
       csv
       haml (~> 6.0)
       middleman (~> 4.0)
@@ -82,8 +83,8 @@ GEM
     http_parser.rb (0.8.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.4.0)
-      rexml
+    kramdown (2.5.1)
+      rexml (>= 3.3.9)
     libv8-node (18.16.0.0-aarch64-linux)
     libv8-node (18.16.0.0-arm64-darwin)
     listen (3.9.0)
@@ -145,12 +146,12 @@ GEM
       rouge (~> 3.2)
     mini_racer (0.8.0)
       libv8-node (~> 18.16.0.0)
-    minitest (5.25.1)
+    minitest (5.25.4)
     multi_json (1.15.0)
-    mutex_m (0.2.0)
-    nokogiri (1.16.7-aarch64-linux)
+    mutex_m (0.3.0)
+    nokogiri (1.18.3-aarch64-linux-gnu)
       racc (~> 1.4)
-    nokogiri (1.16.7-arm64-darwin)
+    nokogiri (1.18.3-arm64-darwin)
       racc (~> 1.4)
     openapi3_parser (0.9.2)
       commonmarker (~> 0.17)
@@ -163,21 +164,21 @@ GEM
     parslet (2.0.0)
     public_suffix (6.0.1)
     racc (1.8.1)
-    rack (2.2.10)
+    rack (2.2.11)
     rack-livereload (0.3.17)
       rack
     rake (13.2.1)
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
-    redcarpet (3.6.0)
-    rexml (3.3.9)
+    redcarpet (3.6.1)
+    rexml (3.4.1)
     rouge (3.30.0)
     sass (3.4.25)
-    sass-embedded (1.80.7-aarch64-linux-gnu)
-      google-protobuf (~> 4.28)
-    sass-embedded (1.80.7-arm64-darwin)
-      google-protobuf (~> 4.28)
+    sass-embedded (1.85.1-aarch64-linux-gnu)
+      google-protobuf (~> 4.29)
+    sass-embedded (1.85.1-arm64-darwin)
+      google-protobuf (~> 4.29)
     sassc (2.4.0)
       ffi (~> 1.9)
     sassc-embedded (1.78.0)
@@ -187,7 +188,7 @@ GEM
       concurrent-ruby (~> 1.0)
       rack (>= 2.2.4, < 4)
     temple (0.10.3)
-    terser (1.2.4)
+    terser (1.2.5)
       execjs (>= 0.3.0, < 3)
     thor (1.2.2)
     tilt (2.0.11)
@@ -197,14 +198,14 @@ GEM
       concurrent-ruby (~> 1.0)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
-    webrick (1.9.0)
+    webrick (1.9.1)
 
 PLATFORMS
   aarch64-linux
   arm64-darwin-23
 
 DEPENDENCIES
-  govuk_tech_docs (~> 4.1.1)
+  govuk_tech_docs (~> 4.1.2)
   mini_racer (~> 0.8.0)
 
 BUNDLED WITH