absolutely forgot the license header

Author: iximeow

phd-tests/framework/src/test_vm/metrics.rs

@@ -1,3 +1,7 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
 use std::net::SocketAddr;
 use std::time::Duration;