[symfony#6281] Reword other items a little bit

Author: wouterj

book/forms.rst

@@ -267,14 +267,8 @@ possible paths:
    recognizes this and immediately writes the submitted data back into the
    ``task`` and ``dueDate`` properties of the ``$task`` object. Then this object
    is validated. If it is invalid (validation is covered in the next section),
-   :method:`Symfony\\Component\\Form\\FormInterface::isValid` returns ``false``
-   again, so the form is rendered together with all validation errors;
-
-   .. note::
-
-       You can use the method :method:`Symfony\\Component\\Form\\FormInterface::isSubmitted`
-       to check whether a form was submitted, regardless of whether or not the
-       submitted data is actually valid.
+   :method:`Symfony\\Component\\Form\\FormInterface::isValid` returns
+   ``false``, so the form is rendered together with all validation errors;
 
 #. When the user submits the form with valid data, the submitted data is again
    written into the form, but this time :method:`Symfony\\Component\\Form\\FormInterface::isValid`