Update setup.py for setuptools 65

setuptools complains loudly if distutils is also used, and exits with error
in the 'docs' step since distutils.core.Command rather than setuptools.Command
was used for that step.

setup.py

@@ -9,9 +9,8 @@
 import subprocess
 import shutil
 import sys
-from distutils.core import Command
 
-from setuptools import setup
+from setuptools import setup, Command
 
 # Manage version number ######################################
 with open(os.path.join("src", "sas", "sasview", "__init__.py")) as fid: