minor #4252 Removed unnecessary comma (allejo)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4252).

Discussion
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Removed unnecessary comma

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | no
| Applies to    | all
| Fixed tickets |

My first pull request, so I'm not entirely sure if I did this right. Anyhow, as the title suggests, the comma doesn't belong in this sentence.

Commits
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a4190bd Removed unnecessary comma

cookbook/security/entity_provider.rst

@@ -367,7 +367,7 @@ fetch the user from the database before checking the password validity.
 .. note::
 
     By default, the entity provider uses the default entity manager to fetch
-    user information from the database. If you,
+    user information from the database. If you
     :doc:`use multiple entity managers </cookbook/doctrine/multiple_entity_managers>`,
     you can specify which manager to use with the ``manager_name`` option: