Fix static functions loop using class' functions

Besides being incorrect, it also caused a hard editor crash for purely
static classes or classes with more static functions than methods.

modules/gdscript/language_server/gdscript_extend_parser.cpp

@@ -757,7 +757,7 @@ Dictionary ExtendGDScriptParser::dump_class_api(const GDScriptParser::ClassNode
 
 	Array static_functions;
 	for (int i = 0; i < p_class->static_functions.size(); ++i) {
-		static_functions.append(dump_function_api(p_class->functions[i]));
+		static_functions.append(dump_function_api(p_class->static_functions[i]));
 	}
 	class_api["static_functions"] = static_functions;