docs: improve style in an example

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Doc/library/imaplib.rst

@@ -333,9 +333,8 @@ An :class:`IMAP4` instance has the following methods:
 
    Example::
 
-      with M.idle(dur=29*60) as idler:
-          for response in idler:
-              typ, datum = response
+      with M.idle(dur=29 * 60) as idler:
+          for type, datum in idler:
               print(typ, datum)
 
       ('EXISTS', b'1')