Update facade docblocks

Author: taylorotwell

src/Illuminate/Support/Facades/DB.php

@@ -105,7 +105,7 @@
  * @method static string getServerVersion()
  * @method static void resolverFor(string $driver, \Closure $callback)
  * @method static \Closure|null getResolver(string $driver)
- * @method static mixed transaction(\Closure $callback, int $attempts = 1)
+ * @method static void transaction(\Closure $callback, int $attempts = 1)
  * @method static void beginTransaction()
  * @method static void commit()
  * @method static void rollBack(int|null $toLevel = null)