minor #6204 Expected: semicolon (cn007b)

This PR was submitted for the 3.0 branch but it was merged into the 2.8 branch instead (closes #6204).

Discussion
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Expected: semicolon

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

Added missed semicolon.

Commits
-------

ab2f9aa Expected: semicolon

cookbook/security/api_key_authentication.rst

@@ -308,7 +308,7 @@ you can use to create an error ``Response``.
                 // this contains information about *why* authentication failed
                 // use it, or return your own message
                 strtr($exception->getMessageKey(), $exception->getMessageData())
-            , 403)
+            , 403);
         }
     }