Add \ReturnTypeWillChange attribute to methods inherited from native interfaces

- Part of https://github.com/friendica/friendica/issues/12011#issuecomment-1321796513

src/Object/Email.php

@@ -200,6 +200,7 @@ class Email implements IEmail
 	/**
 	 * @inheritDoc
 	 */
+	#[\ReturnTypeWillChange]
 	public function jsonSerialize()
 	{
 		return $this->toArray();