Fix wrong documented type

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

lib/Model/IMAPMessage.php

@@ -145,7 +145,7 @@ class IMAPMessage implements IMessage, JsonSerializable {
 	}
 
 	/**
-	 * @param string $flags
+	 * @param array $flags
 	 *
 	 * @throws Exception
 	 *

lib/Model/IMessage.php

@@ -46,7 +46,7 @@ interface IMessage {
 	public function getFlags(): array;
 
 	/**
-	 * @param string $flags
+	 * @param array $flags
 	 */
 	public function setFlags(array $flags);