Update to laravel 7

vendor/symfony/mime/Header/IdentificationHeader.php

@@ -18,8 +18,6 @@ use Symfony\Component\Mime\Exception\RfcComplianceException;
  * An ID MIME Header for something like Message-ID or Content-ID (one or more addresses).
  *
  * @author Chris Corbyn
- *
- * @experimental in 4.3
  */
 final class IdentificationHeader extends AbstractHeader
 {
@@ -46,10 +44,7 @@ final class IdentificationHeader extends AbstractHeader
         $this->setId($body);
     }
 
-    /**
-     * @return array
-     */
-    public function getBody()
+    public function getBody(): array
     {
         return $this->getIds();
     }