Dependency - Redcarpet 3.5.1 -> 3.6.0

Offers two fixes:

* Match fence char and length when matching closing fence in fenced code
  blocks (Fixes #208)
* Fix anchor generation on titles with ampersands (Fixes #696).

And three improvements:

* Avoid warnings running on Ruby 3.2+ (See #721).
* Consider <center> as a block-level element (See #702).
* Properly provide a third argument to the table_cell callback
  indicating whether the current cell is part of the header or not. The
  previous implementation with two parameters is still supported (See
  #604 and #605).

Of particular interest to me here is the removal of Ruby 3.2 warnings
which are becoming relevant as tech docs apps are upgraded

See changelong:
https://github.com/vmg/redcarpet/releases/tag/v3.6.0

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+Updates to dependencies including:
+
+- Redcarpet to v3.6.0, removing warnings that appear in Tech Docs sites running Ruby 3.2+
+
 ## 3.5.0
 
 ### New features

govuk_tech_docs.gemspec

@@ -47,7 +47,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "middleman-syntax", "~> 3.2.0"
   spec.add_dependency "nokogiri"
   spec.add_dependency "openapi3_parser", "~> 0.9.0"
-  spec.add_dependency "redcarpet", "~> 3.5.1"
+  spec.add_dependency "redcarpet", "~> 3.6.0"
 
   spec.add_development_dependency "byebug"
   spec.add_development_dependency "capybara", "~> 3.32"