Fix linter

pystencils/gpu/kernelcreation.py

 from typing import Union
 
-import numpy as np
-
 from pystencils.astnodes import Block, KernelFunction, LoopOverCoordinate, SympyAssignment
 from pystencils.config import CreateKernelConfig
 from pystencils.typing import StructType, TypedSymbol