Change to a test value that will certainly ever happen

String literals are not reliable to expect errors on since
the spec may change and accept `string`

types/jss/jss-tests.ts

@@ -70,7 +70,7 @@ styleSheet.addRule('badProperty', {
 });
 
 styleSheet.addRule('badValue', { // $ExpectError
-	'align-items': 'thisIsNotAValidValue',
+	'align-items': Symbol(),
 });
 
 styleSheet.detach();