Let setuptools use its own build_ext command

Required for editable installation

setup.py

@@ -4,7 +4,6 @@ from subprocess import check_output
 
 import numpy
 from Cython.Build import cythonize
-from Cython.Distutils import build_ext
 from setuptools import find_packages, setup
 from setuptools.extension import Extension
 
@@ -143,7 +142,6 @@ setup(
     },
     cmdclass={
         "build": PreInstallCommand,
-        "build_ext": build_ext,
     },
     ext_modules=cythonize(ext_modules, language_level=3),
     install_requires=install_requires,