Don't create a new list of qubits in Gate.on (#6390)

Review: @dabacon

Author: maffoo

cirq-core/cirq/ops/raw_types.py

@@ -230,7 +230,7 @@ def on(self, *qubits: Qid) -> 'Operation':
         Returns: a `cirq.Operation` which is this gate applied to the given
             qubits.
         """
-        return ops.gate_operation.GateOperation(self, list(qubits))
+        return ops.gate_operation.GateOperation(self, qubits)
 
     def on_each(self, *targets: Union[Qid, Iterable[Any]]) -> List['cirq.Operation']:
         """Returns a list of operations applying the gate to all targets.