Ignore RequiredRubyVersion rubocop warning

Bumping required Ruby version to 3.1.x as there are no apps that I've
found using lower versions, however a number of apps are still on 3.1.x
so silencing the warning until we specify the required version to be
3.2.x. 3.1.x is still compatible with 3.2.x from the testing matrix and
testing a couple apps manually.

.github/workflows/ci.yml

@@ -17,8 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: ['3.0', 3.1, 3.2]
+        ruby: [3.1, 3.2]
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4

govuk_publishing_components.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |s|
   s.description = "A gem to document components in GOV.UK frontend applications"
   s.homepage    = "https://github.com/alphagov/govuk_publishing_components"
   s.license     = "MIT"
-  s.required_ruby_version = ">= 3.0"
+  s.required_ruby_version = ">= 3.1" # rubocop:disable Gemspec/RequiredRubyVersion
 
   s.files = Dir["{node_modules/govuk-frontend,node_modules/axe-core,node_modules/sortablejs,app,config,db,lib}/**/*", "LICENCE.md", "README.md"]