Fix lint: add noqa for re-exported packaging symbols

Added # noqa: F401 to packaging imports in platforms/_utils.py
to suppress 'imported but unused' warnings for symbols that are
being re-exported for backward compatibility.

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Co-Authored-By: Claude <[email protected]>

Author: robtaylor

chipflow_lib/platforms/_utils.py

@@ -28,7 +28,7 @@
 
 # Import packaging functionality from new module
 # These are re-exported for backward compatibility
-from ..packaging import (
+from ..packaging import (  # noqa: F401
     Pin, PinSet, PinList, Pins,
     PowerType, JTAGWire, PortType,
     PowerPins, JTAGPins, BringupPins,