CommandEnum: specify enumValues type

phpstan 0.12.26 starts reporting errors about the result of array_search() being given to some constructor or another because of the lack of key type specification.

src/pocketmine/network/mcpe/protocol/types/CommandEnum.php

@@ -26,7 +26,10 @@ namespace pocketmine\network\mcpe\protocol\types;
 class CommandEnum{
 	/** @var string */
 	public $enumName;
-	/** @var string[] */
+	/**
+	 * @var string[]
+	 * @phpstan-var list<string>
+	 */
 	public $enumValues = [];
 
 }