Docs: Fix a typo in idle.rst (Chitespace -> Whitespace) (pythonGH-140946)

Fix typo in idle.rst
(cherry picked from commit b373d34)

Co-authored-by: Yongzi Li <[email protected]>

Author: Yzi-Li

Doc/library/idle.rst

@@ -204,7 +204,7 @@ New Indent Width
    Open a dialog to change indent width. The accepted default by the Python
    community is 4 spaces.
 
-Strip Trailing Chitespace
+Strip Trailing Whitespace
    Remove trailing space and other whitespace characters after the last
    non-whitespace character of a line by applying str.rstrip to each line,
    including lines within multiline strings.  Except for Shell windows,