Fix references in docs

Co-authored-by: Adam Turner <[email protected]>

Author: srittau

Doc/library/typing.rst

@@ -2818,7 +2818,7 @@ ABCs and Protocols for working with I/O
    :func:`open`. Please note that these classes are not protocols, and
    their interface is fairly broad.
 
-The protocols :class:`.io.Reader` and :class:`.io.Writer` offer a simpler
+The protocols :class:`io.Reader` and :class:`io.Writer` offer a simpler
 alternative for argument types, when only the ``read()`` or ``write()``
 methods are accessed, respectively::