minor #5130 [Cookbook][Security] Fiyed typo in entity_provider.rst (althaus)

This PR was submitted for the 2.6 branch but it was merged into the 2.3 branch instead (closes #5130).

Discussion
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[Cookbook][Security] Fiyed typo in entity_provider.rst

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | n/a

Fixed typo in the AdvancedUserInterface section.

Commits
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f0722c9 Update entity_provider.rst

Author: wouterj

cookbook/security/entity_provider.rst

@@ -321,7 +321,7 @@ If a User's ``isActive`` property is set to ``false`` (i.e. ``is_active``
 is 0 in the database), the user will still be able to login to the site
 normally. This is easily fixable.
 
-To exclude inactive users, change your ``User`` clas to implement
+To exclude inactive users, change your ``User`` class to implement
 :class:`Symfony\\Component\\Security\\Core\\User\\AdvancedUserInterface`.
 This extends :class:`Symfony\\Component\\Security\\Core\\User\\UserInterface`,
 so you only need the new interface::