[3.13] Add missing comma to tuple in except* docs (GH-142395) (#142684)

Co-authored-by: dr-carlos <77367421+dr-carlos@users.noreply.github.com>

Author: miss-islington

Doc/reference/compound_stmts.rst

@@ -385,7 +385,7 @@ type of the target ``e`` is consistently :exc:`BaseExceptionGroup`::
    ... except* BlockingIOError as e:
    ...     print(repr(e))
    ...
-   ExceptionGroup('', (BlockingIOError()))
+   ExceptionGroup('', (BlockingIOError(),))
 
 :keyword:`break`, :keyword:`continue` and :keyword:`return`
 cannot appear in an :keyword:`!except*` clause.