minor symfony#57975 [Mime] remove constructor argument type-hint (xabbuh)

This PR was merged into the 7.1 branch.

Discussion
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[Mime] remove constructor argument type-hint

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        |
| License       | MIT

The child class Message does not call the parent constructor which means that the $message property will never be initialized when using CPP.

Commits
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b492f70 remove constructor argument type-hint

Author: xabbuh

src/Symfony/Component/Mime/RawMessage.php

@@ -24,7 +24,7 @@ class RawMessage
      * @param iterable<string>|string|resource $message
      */
     public function __construct(
-        private mixed $message,
+        private $message,
     ) {
     }