add missing method doc (#36367)

Author: tomirons

src/Illuminate/Support/Facades/ParallelTesting.php

@@ -5,6 +5,7 @@
 /**
  * @method static void setUpProcess(callable $callback)
  * @method static void setUpTestCase(callable $callback)
+ * @method static void setupTestDatabase(callable $callback)
  * @method static void tearDownProcess(callable $callback)
  * @method static void tearDownTestCase(callable $callback)
  * @method static int|false token()