minor #13199 remove link to the already deleted propel1 bridge (W0rma)

This PR was merged into the 3.4 branch.

Discussion
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remove link to the already deleted propel1 bridge

`Symfony\Bridge\Propel1\Form\PropelTypeGuesser` was removed long time ago. Therefore it should be removed from the docs, too.

Commits
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3709c5a remove link to the already deleted propel1 bridge

Author: javiereguiluz

form/type_guesser.rst

@@ -13,8 +13,6 @@ type guessers.
 
     Symfony also provides some form type guessers in the bridges:
 
-    * :class:`Symfony\\Bridge\\Propel1\\Form\\PropelTypeGuesser` provided by
-      the Propel1 bridge;
     * :class:`Symfony\\Bridge\\Doctrine\\Form\\DoctrineOrmTypeGuesser`
       provided by the Doctrine bridge.