minor #12767 Update messenger.rst (erop)

This PR was submitted for the master branch but it was merged into the 4.3 branch instead (closes #12767).

Discussion
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Update messenger.rst

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Commits
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00d045c Update messenger.rst

Author: wouterj

messenger.rst

@@ -1310,7 +1310,7 @@ middleware and *only* include your own:
                 buses:
                     messenger.bus.default:
                         middleware:
-                            # service ids that implement Symfony\Component\Messenger\Middleware
+                            # service ids that implement Symfony\Component\Messenger\Middleware\MiddlewareInterface
                             - 'App\Middleware\MyMiddleware'
                             - 'App\Middleware\AnotherMiddleware'