Clarified the tempfile.tempdir documentation (GH-7829) (GH-7841)

(cherry picked from commit 940ae608566fd4446ff92a22705f646cde1d087c)

Co-authored-by: Srinivas Reddy Thatiparthy (శ్రీనివాస్ రెడ్డి తాటిపర్తి) <srinivasreddy@users.noreply.github.com>
diff --git a/Doc/library/tempfile.rst b/Doc/library/tempfile.rst
index c59aca1..0d0da4d 100644
--- a/Doc/library/tempfile.rst
+++ b/Doc/library/tempfile.rst
@@ -253,7 +253,7 @@
    default value for the *dir* argument to the functions defined in this
    module.
 
-   If ``tempdir`` is unset or ``None`` at any call to any of the above
+   If ``tempdir`` is ``None`` (the default) at any call to any of the above
    functions except :func:`gettempprefix` it is initialized following the
    algorithm described in :func:`gettempdir`.