Add actingAsGuest method for clearing actingAs calls

Author: michaelnabil230

src/Authentication.php

@@ -17,6 +17,16 @@ function actingAs(Authenticatable $user, ?string $driver = null)
     return test()->actingAs(...func_get_args());
 }
 
+/**
+ * Clear the currently logged in user for the application.
+ *
+ * @return TestCase
+ */
+function actingAsGuest(?string $guard = null)
+{
+    return test()->actingAsGuest(...func_get_args());
+}
+
 /**
  * Set the currently logged in user for the application.
  *