minor #8389 Add a note about bundle inheritance deprecation (fabpot)

This PR was merged into the 3.4 branch.

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Add a note about bundle inheritance deprecation

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fa3b822 added a note about bundle inheritance deprecation

Author: xabbuh

bundles/inheritance.rst

@@ -4,6 +4,11 @@
 How to Use Bundle Inheritance to Override Parts of a Bundle
 ===========================================================
 
+.. caution::
+
+    Bundle inheritance is deprecated since Symfony 3.4 and will be removed in
+    4.0.
+
 When working with third-party bundles, you'll probably come across a situation
 where you want to override a file in that third-party bundle with a file
 in one of your own bundles. Symfony gives you a very convenient way to override