minor #17294 [Cache] Tip to not reconfigure system cache (gnito-org)

This PR was merged into the 4.4 branch.

Discussion
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[Cache] Tip to not reconfigure system cache

Add tip to not reconfigure system cache as per `@nicolas`-grekas [comment](#12774 (comment)).

Commits
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aa67292 [Cache] Tip to not reconfigure system cache

Author: javiereguiluz

cache.rst

@@ -101,6 +101,11 @@ adapter (template) they use by using the ``app`` and ``system`` key like:
             ]);
         };
 
+.. tip::
+
+    While it is possible to reconfigure the system cache, it is not recommended, because
+    the default is really the best possible configuration.
+
 The Cache component comes with a series of adapters pre-configured:
 
 * :doc:`cache.adapter.apcu </components/cache/adapters/apcu_adapter>`