minor #11624 Deprecate the LoggingMiddleware in Symfony 4.3 (javiereguiluz)

This PR was merged into the 4.3 branch.

Discussion
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Deprecate the LoggingMiddleware in Symfony 4.3

In #11619 we removed this for Symfony 5.0 ... but we also need to add the deprecation notice in 4.3.

Commits
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d28cfd3 Deprecate the LoggingMiddleware in Symfony 4.3

Author: javiereguiluz

components/messenger.rst

@@ -79,6 +79,11 @@ are configured for you:
 #. :class:`Symfony\\Component\\Messenger\\Middleware\\SendMessageMiddleware` (enables asynchronous processing)
 #. :class:`Symfony\\Component\\Messenger\\Middleware\\HandleMessageMiddleware` (calls the registered handler(s))
 
+.. deprecated:: 4.3
+
+    The ``LoggingMiddleware`` is deprecated since Symfony 4.3 and will be
+    removed in 5.0. Pass a logger to ``SendMessageMiddleware`` instead.
+
 Example::
 
     use App\Message\MyMessage;