PEP 751: make path/url optional (#4108)

Author: brettcannon

peps/pep-0751.rst

@@ -499,15 +499,15 @@ See ``groups.requirements.marker``.
 ``packages.sdist.url``
 ''''''''''''''''''''''
 
-- Required if ``path`` is not set
+- Optional; mutually-exclusive with ``path``
 - String
 - The URL to the file.
 
 
 ``packages.sdist.path``
 '''''''''''''''''''''''
 
-- Required if ``url`` is not set
+- Optional; mutually-exclusive with ``url``
 - String
 - A path to the file, which may be absolute or relative.
 - If the path is relative it MUST be relative to the lock file.