simplify without composer install

src/Autocomplete/doc/index.rst

@@ -33,14 +33,9 @@ needed if you're using AssetMapper):
 Usage in a Form (without Ajax)
 ------------------------------
 
-Any ``ChoiceType`` or ``EntityType`` can be transformed into a
-Tom Select-powered UI control by adding the ``autocomplete`` option.
-
-In a new project you may need to install `Symfony Form`_:
-
-.. code-block:: terminal
-
-    $ composer require symfony/form
+If you're using `Symfony Form`_ any ``ChoiceType`` or ``EntityType`` can be
+transformed into a Tom Select-powered UI control by adding the ``autocomplete``
+option:
 
 .. code-block:: diff