minor #13762 Update messenger.rst (atailouloute)

This PR was merged into the 4.4 branch.

Discussion
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Update messenger.rst

Fix php example (unexpected double arrow)

Commits
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b660849 Update messenger.rst

Author: javiereguiluz

messenger.rst

@@ -953,7 +953,7 @@ The transport has a number of options:
         $container->loadFromExtension('framework', [
             'messenger' => [
                 'transports' => [
-                    'async_priority_high' => 'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%?queue_name=high_priority',
+                    'async_priority_high' => '%env(MESSENGER_TRANSPORT_DSN)%?queue_name=high_priority',
                     'async_priority_low' => [
                         'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%',
                         'options' => [