Remove unused import

Author: migueltorrescosta

cirq-core/cirq/ops/permutation_gate.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict, Iterable, Sequence, Tuple, TYPE_CHECKING
+from typing import Any, Dict, Sequence, Tuple, TYPE_CHECKING
 
 from cirq import protocols, value
 from cirq.ops import raw_types, swap_gates