Try fix PHP 7.4 CI issues

Author: janedbal

tests/PHPStan/Reflection/Deprecation/data/CustomDeprecationProvider.php

@@ -1,4 +1,6 @@
-<?php declare(strict_types = 1);
+<?php // lint >= 8.0
+
+declare(strict_types = 1);
 
 namespace PHPStan\Tests;
 

tests/PHPStan/Reflection/Deprecation/data/deprecations.php

@@ -5,9 +5,12 @@
 #[\Attribute(\Attribute::TARGET_ALL)]
 class CustomDeprecated {
 
+	public ?string $description;
+
 	public function __construct(
-		public ?string $description = null,
+		?string $description = null,
 	) {
+		$this->description = $description;
 	}
 }