Update file_save.php (#4591)

file_save.php

@@ -60,7 +60,7 @@
 		case 'php':
 			$edit_directory = $_SERVER["DOCUMENT_ROOT"].'/'.PROJECT_PATH;
 			break;
-		case 'grammer':
+		case 'grammar':
 			$edit_directory = $_SESSION['switch']['grammar']['dir'];
 			break;
 		case 'provision':