4.0 | Remove previously deprecated code #849

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::$checkClasses - deprecated since VIPCS 3.1.0, see Classes/DeclarationCompatibility: various sniff improvements #858, related to Audit Public Sniff Properties #234.
• WordPressVIPMinimum\Sniffs\Classes\DeclarationCompatibilitySniff::$checkClassesGroups - deprecated since VIPCS 3.1.0, see Classes/DeclarationCompatibility: various sniff improvements #858, related to Audit Public Sniff Properties #234.
• The complete WordPressVIPMinimum\Sniffs\Functions\DynamicCalls sniff - deprecated since VIPCS 3.1.0, see Remove ~~Review~~ the WordPressVIPMinimum.Functions.DynamicCalls sniff #517 and Hard-deprecate the WordPressVIPMinimum.Functions.DynamicCalls sniff #865
• WordPressVIPMinimum\Sniffs\Performance\TaxonomyMetaInOptionsSniff::$option_functions - deprecated since VIPCS 3.1.0, see Performance/TaxonomyMetaInOptions: various improvements #872, related to Audit Public Sniff Properties #234.
• WordPressVIPMinimum\Sniffs\Security\ProperEscapingFunctionSniff::$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