style: drop unused yaml import in assemble tests

Author: Ronald Tse

tests/test_assemble_release.py

@@ -7,8 +7,6 @@
 from pathlib import Path
 from threading import Thread
 
-import yaml
-
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent / "scripts"))
 
 from assemble_release import assemble  # noqa: E402