minor #20188 bundles - add reason why they are not recommended (landsman)

This PR was submitted for the 6.4 branch but it was squashed and merged into the 5.4 branch instead.

Discussion
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bundles - add reason why they are not recommended

I was missing a link for reasoning why this was deprecated. Please add this missing context.

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Commits
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2a0a716 bundles - add reason why they are not recommended

Author: OskarStark

best_practices.rst

@@ -160,6 +160,8 @@ values is that it's complicated to redefine their values in your tests.
 Business Logic
 --------------
 
+.. _best-practice-no-application-bundles:
+
 Don't Create any Bundle to Organize your Application Logic
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

bundles.rst

@@ -6,7 +6,7 @@ The Bundle System
 .. caution::
 
     In Symfony versions prior to 4.0, it was recommended to organize your own
-    application code using bundles. This is no longer recommended and bundles
+    application code using bundles. This is :ref:`no longer recommended <best-practice-no-application-bundles>` and bundles
     should only be used to share code and features between multiple applications.
 
 A bundle is similar to a plugin in other software, but even better. The core