4.0 | Remove previously deprecated code

Removing the deprecated JS sniffs is tracked separately in #442.

List of deprecated code which should be removed in the next major:
- [ ] `WordPressVIPMinimum\Sniffs\Classes\DeclarationCompatibilitySniff::$checkClasses` - deprecated since VIPCS 3.1.0, see #858, related to #234.
- [ ] `WordPressVIPMinimum\Sniffs\Classes\DeclarationCompatibilitySniff::$checkClassesGroups` - deprecated since VIPCS 3.1.0, see #858, related to #234.
- [ ] The complete `WordPressVIPMinimum\Sniffs\Functions\DynamicCalls` sniff - deprecated since VIPCS 3.1.0, see #517 and #865
- [ ] `WordPressVIPMinimum\Sniffs\Performance\TaxonomyMetaInOptionsSniff::$option_functions` - deprecated since VIPCS 3.1.0, see #872, related to #234.
- [ ] `WordPressVIPMinimum\Sniffs\Security\ProperEscapingFunctionSniff::$url_attrs` - deprecated since VIPCS 2.3.1
- [ ] `WordPressVIPMinimum\Sniffs\Security\ProperEscapingFunctionSniff::$attr_endings` - deprecated since VIPCS 2.3.1
- [ ] `WordPressVIPMinimum\Sniffs\Security\ProperEscapingFunctionSniff::attr_expects_url)_` - deprecated since VIPCS 2.3.1
- [ ] `WordPressVIPMinimum\Sniffs\Security\ProperEscapingFunctionSniff::is_html_attr()` - deprecated since VIPCS 2.3.1

Comienza inspeccionando los sniffs de WordPressVIPMinimum indicados y sus miembros obsoletos; después, revisa las issues referenciadas #858, #234, #517, #865 y #872 para conocer el alcance y las dependencias. Los sniffs de JavaScript se siguen por separado en #442. Se considera terminado cuando se haya eliminado el código PHP obsoleto indicado, sin incluir ese trabajo separado.

Escrito por el modelo de indexación a partir del texto del issue.