gh-153934: Correct documented paramemeter in calendar.weekheader from n to width (GH-153942)

(cherry picked from commit 7486c7b)

Co-authored-by: Marta <marta.podziewska@gmail.com>

Author: podmar

Doc/library/calendar.rst

@@ -392,9 +392,9 @@ For simple text calendars this module provides the following functions.
    *month* (``1``--``12``), *day* (``1``--``31``).
 
 
-.. function:: weekheader(n)
+.. function:: weekheader(width)
 
-   Return a header containing abbreviated weekday names. *n* specifies the width in
+   Return a header containing abbreviated weekday names. *width* specifies the width in
    characters for one weekday.