put call to unsorted params outside of loop (#6112)

Co-authored-by: Matthew Treinish <[email protected]>

qiskit/circuit/quantumcircuit.py

@@ -2016,10 +2016,11 @@ def assign_parameters(self, parameters, inplace=False,
         if isinstance(parameters, dict):
             # unroll the parameter dictionary (needed if e.g. it contains a ParameterVector)
             unrolled_param_dict = self._unroll_param_dict(parameters)
+            unsorted_parameters = self._unsorted_parameters()
 
             # check that all param_dict items are in the _parameter_table for this circuit
             params_not_in_circuit = [param_key for param_key in unrolled_param_dict
-                                     if param_key not in self._unsorted_parameters()]
+                                     if param_key not in unsorted_parameters]
             if len(params_not_in_circuit) > 0:
                 raise CircuitError('Cannot bind parameters ({}) not present in the circuit.'.format(
                     ', '.join(map(str, params_not_in_circuit))))