minor #18887 Corrected missing property promotion. (miqrogroove)

This PR was merged into the 6.3 branch.

Discussion
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Corrected missing property promotion.

Fixes #18886 .

Promoted the constructor parameter to a private property to fix the example code.

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Commits
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6be0972 Corrected missing property promotion.

Author: javiereguiluz

service_container/autowiring.rst

@@ -694,7 +694,7 @@ attribute::
     {
         public function __construct(
             #[AutowireServiceClosure('third_party.remote_message_formatter')]
-            \Closure $messageFormatterResolver
+            private \Closure $messageFormatterResolver
         ) {
         }