package/python-typing-extensions: update homepage link in help

Typing-extensions has moved to a separate repository, the previous
link now leads to a 404 page. The top level README in the previous
repository points at the new one, see:
https://github.com/python/typing/blob/fafcdeb724ac22ace877bee4485ed3b4c3edbbd8/README.md#repository-content

Signed-off-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/python-typing-extensions/Config.in

@@ -3,4 +3,4 @@ config BR2_PACKAGE_PYTHON_TYPING_EXTENSIONS
 	help
 	  Backported and Experimental Type Hints for Python 3.5+.
 
-	  https://github.com/python/typing/blob/master/typing_extensions/README.rst
+	  https://github.com/python/typing_extensions