Disable GDScript warning for unused class variable by default

modules/gdscript/gdscript.cpp

@@ -2143,7 +2143,8 @@ GDScriptLanguage::GDScriptLanguage() {
 	GLOBAL_DEF("debug/gdscript/completion/autocomplete_setters_and_getters", false);
 	for (int i = 0; i < (int)GDScriptWarning::WARNING_MAX; i++) {
 		String warning = GDScriptWarning::get_name_from_code((GDScriptWarning::Code)i).to_lower();
-		GLOBAL_DEF("debug/gdscript/warnings/" + warning, !warning.begins_with("unsafe_"));
+		bool default_enabled = !warning.begins_with("unsafe_") && i != GDScriptWarning::UNUSED_CLASS_VARIABLE;
+		GLOBAL_DEF("debug/gdscript/warnings/" + warning, default_enabled);
 	}
 #endif // DEBUG_ENABLED
 }