minor #13082 Typo (OskarStark)

This PR was merged into the 5.0 branch.

Discussion
----------

Typo

<!--

If your pull request fixes a BUG, use the oldest maintained branch that contains
the bug (see https://symfony.com/roadmap for the list of maintained branches).

If your pull request documents a NEW FEATURE, use the same Symfony branch where
the feature was introduced (and `master` for features of unreleased versions).

-->

Commits
-------

8a6e178 Typo

Author: wouterj

notifier.rst

@@ -56,7 +56,7 @@ Twilio   ``symfony/twilio-notifier``  ``twilio://SID:TOKEN@default?from=FROM``
 Nexmo    ``symfony/nexmo-notifier``   ``nexmo://KEY:SECRET@default?from=FROM``
 =======  ===========================  ========================================
 
-To enable a texter, add the add the correct DSN in your ``.env`` file and
+To enable a texter, add the correct DSN in your ``.env`` file and
 configure the ``texter_transports``:
 
 .. code-block:: bash