Fix typos

Author: pierredup

form/unit_testing.rst

@@ -163,7 +163,7 @@ Forms Using Validation
 If your forms uses the ``invalid_message`` or ``constraints`` option for validation, you need to
 register the validation extension which provides this options.
 Luckily Symfony provides a custom test class which does this for you.
-In order to have this option registered, your test needs to extend from the
+In order to have these options registered, your test needs to extend the
 :class:`Symfony\\Component\\Form\\Tests\\Extension\\Validator\\Type\\TypeTestCase`
 class::