Fix lint for release/util.py

Introduced in ea49fa3

Seen in https://buildkite.com/materialize/test/builds/89108#019187f5-9456-41fd-bcf3-a5acdadcd7fa

misc/python/materialize/release/util.py

@@ -1,3 +1,12 @@
+# Copyright Materialize, Inc. and contributors. All rights reserved.
+#
+# Use of this software is governed by the Business Source License
+# included in the LICENSE file at the root of this repository.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0.
+
 """Utilities for release management."""
 
 from pathlib import Path