LibXML: Remove declarations for non-existent methods

Author: https://github.com/AtkinsSJ
Commit: 8dff4c577f
Pull-request: https://github.com/SerenityOS/serenity/pull/17203
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibXML/Parser/Parser.h

@@ -83,7 +83,6 @@ private:
         Content,
     };
     ErrorOr<DeprecatedString, ParseError> resolve_reference(EntityReference const&, ReferencePlacement);
-    ErrorOr<DeprecatedString, ParseError> resolve_parameter_entity_reference(EntityReference const&);
 
     enum class Required {
         No,