minor #12304 fixing that exchange then name is needed (weaverryan)

This PR was merged into the 4.3 branch.

Discussion
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fixing that exchange then name is needed

Hi!

The PR clarifies that you need `exchange` and then `name` for amqp (just did it in a project). And redis is `group` not group1

Commits
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16bc0fe fixing that exchange then name is needed

Author: javiereguiluz

messenger.rst

@@ -501,8 +501,12 @@ different messages to them. For example:
                         dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
                         options:
                             # queue_name is specific to the doctrine transport
-                            # try "exchange" for amqp or "group1" for redis
                             queue_name: high
+
+                            # for amqp
+                            #exchange:
+                            #    name: high
+                            # or redis try "group"
                     async_priority_low:
                         dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
                         options: