bpo-32413: Add documentation that at the module level, locals(), globals() are the same dictionary (GH-5004)

https://bugs.python.org/issue32413

Doc/library/functions.rst

@@ -843,7 +843,8 @@ are always available.  They are listed here in alphabetical order.
 
    Update and return a dictionary representing the current local symbol table.
    Free variables are returned by :func:`locals` when it is called in function
-   blocks, but not in class blocks.
+   blocks, but not in class blocks. Note that at the module level, :func:`locals`
+   and :func:`globals` are the same dictionary.
 
    .. note::
       The contents of this dictionary should not be modified; changes may not