Docs: don't say cdef functions exist in module dict (#4865)

Patch is against 0.29.x branch (to fix both versions of the
documentation).

docs/src/userguide/sharing_declarations.rst

@@ -166,13 +166,6 @@ example:
 
 .. literalinclude:: ../../examples/userguide/sharing_declarations/spammery.pyx
 
-.. note::
-
-    When a module exports a C function in this way, an object appears in the
-    module dictionary under the function's name. However, you can't make use of
-    this object from Python, nor can you use it from Cython using a normal import
-    statement; you have to use :keyword:`cimport`.
-
 .. _sharing_extension_types:
 
 Sharing Extension Types