bpo-43620: Remove reference to os.sep from os.path.join() doc (#25025)

- removed ambiguous reference to os.sep from os.path.join() doc

Author: jpsutton

Doc/library/os.path.rst

@@ -306,11 +306,10 @@ the :mod:`glob` module.)
 
    Join one or more path components intelligently.  The return value is the
    concatenation of *path* and any members of *\*paths* with exactly one
-   directory separator (``os.sep``) following each non-empty part except the
-   last, meaning that the result will only end in a separator if the last
-   part is empty.  If a component is an absolute path, all previous
-   components are thrown away and joining continues from the absolute path
-   component.
+   directory separator following each non-empty part except the last, meaning
+   that the result will only end in a separator if the last part is empty.  If
+   a component is an absolute path, all previous components are thrown away
+   and joining continues from the absolute path component.
 
    On Windows, the drive letter is not reset when an absolute path component
    (e.g., ``r'\foo'``) is encountered.  If a component contains a drive