LibWeb: Stop generating C++ includes for non-code-generating IDL files

Specifically, IDL files that do not include interface or enumeration
declarations do not generate any code, and as such should not be
included.

Meta/Lagom/Tools/CodeGenerators/LibWeb/WrapperGenerator/IDLParser.h

@@ -52,6 +52,7 @@ private:
     void parse_constant(Interface&);
 
     static HashTable<String> s_all_imported_paths;
+    HashTable<String> required_imported_paths;
     String import_base_path;
     String filename;
     StringView input;