Remove all CSS-specific sniffs

Removes the following sniffs:
- Generic.Debug.CSSLint
- Squiz.CSS.ClassDefinitionClosingBraceSpace
- Squiz.CSS.ClassDefinitionNameSpacing
- Squiz.CSS.ClassDefinitionOpeningBraceSpace
- Squiz.CSS.ColonSpacing
- Squiz.CSS.ColourDefinition
- Squiz.CSS.DisallowMultipleStyleDefinitions
- Squiz.CSS.DuplicateClassDefinition
- Squiz.CSS.DuplicateStyleDefinition
- Squiz.CSS.EmptyClassDefinition
- Squiz.CSS.EmptyStyleDefinition
- Squiz.CSS.ForbiddenStyles
- Squiz.CSS.Indentation
- Squiz.CSS.LowercaseStyleDefinition
- Squiz.CSS.MissingColon
- Squiz.CSS.NamedColours
- Squiz.CSS.Opacity
- Squiz.CSS.SemicolonSpacing
- Squiz.CSS.ShorthandSize

Ref:
* squizlabs/PHP_CodeSniffer 2448

Co-authored-by: jrfnl <jrfnl@users.noreply.github.com>

Author: gsherwood

.github/workflows/test.yml

@@ -200,7 +200,6 @@ jobs:
         if: ${{ matrix.custom_ini == false }}
         run: >
           npm install -g --fund false
-          csslint
           eslint
           jshint
 
@@ -302,7 +301,6 @@ jobs:
         if: ${{ matrix.custom_ini == false }}
         run: >
           npm install -g --fund false
-          csslint
           eslint
           jshint