Update comment for previous change

Author: brianmay

setuptools_scm/version.py

@@ -31,6 +31,7 @@ def callable_or_entrypoint(group, callable_or_name):
 def tag_to_version(tag):
     trace('tag', tag)
     # lstrip the v because of py2/py3 differences in setuptools
+    # also required for old versions of setuptools
     version = tag.rsplit('-', 1)[-1].lstrip('v')
     if parse_version is None:
         return version