minor #4013 Removed wrong reference to cookbook (gquemener)

This PR was merged into the 2.5 branch.

Discussion
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Removed wrong reference to cookbook

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.5
| Fixed tickets |

The /cookbook/request/mime_type article does not contain an example to register a kernel listener since 2.5

Commits
-------

b8f27ef Removed wrong reference to cookbook

reference/dic_tags.rst

@@ -508,9 +508,6 @@ points.
 For a full example of this listener, read the :doc:`/cookbook/service_container/event_listener`
 cookbook entry.
 
-For another practical example of a kernel listener, see the cookbook
-article: :doc:`/cookbook/request/mime_type`.
-
 Core Event Listener Reference
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~