remove more ref to cythonmagic

docs/source/config/extensions/cythonmagic.rst

@@ -4,4 +4,4 b''
 cythonmagic
 ===========
 
-.. automodule:: IPython.extensions.cythonmagic
+The `cython` magic has been moved in the `cython` package.

docs/source/config/extensions/index.rst

@@ -100,3 +100,5 b' Extensions bundled with IPython'
 * ``rmagic`` is now part of `rpy2 <http://rpy.sourceforge.net/>`_. Use
   ``%load_ext rpy2.ipython`` to load it, and see :mod:`rpy2.ipython.rmagic` for
   details of how to use it.
+* ``cythonmagic``used to be bundled, but is now part of `cython <https://github.com/cython/cython/>`_
+  Use ``%load_ext cython`` to load it.

docs/source/config/intro.rst

@@ -41,7 +41,7 b' extend, :meth:`~IPython.config.loader.LazyConfigValue.prepend` (like'
 extend, but at the front), add and update (which works both for dicts
 and sets)::
 
-    c.InteractiveShellApp.extensions.append('cythonmagic')
+    c.InteractiveShellApp.extensions.append('cython')
 
 .. versionadded:: 2.0
    list, dict and set methods for config values