Rename instance()->instantiate() when it's a verb

modules/gdscript/tests/test_gdscript.cpp

@@ -165,7 +165,7 @@ static void test_compiler(const String &p_code, const String &p_script_path, con
 
 	GDScriptCompiler compiler;
 	Ref<GDScript> script;
-	script.instance();
+	script.instantiate();
 	script->set_path(p_script_path);
 
 	err = compiler.compile(&parser, script.ptr(), false);