Doc: Improve wording of os.path.commonpath() (python#122627)

Co-authored-by: Adam Turner <[email protected]>

Author: Matth-M

Doc/library/os.path.rst

@@ -81,7 +81,7 @@ the :mod:`glob` module.)
 
    Return the longest common sub-path of each pathname in the iterable
    *paths*.  Raise :exc:`ValueError` if *paths* contain both absolute
-   and relative pathnames, the *paths* are on the different drives or
+   and relative pathnames, if *paths* are on different drives, or
    if *paths* is empty.  Unlike :func:`commonprefix`, this returns a
    valid path.