Backport PR #5559: Minor typo fix in "Cython Magics.ipynb"

``IPtyhon`` -> ``IPython``

examples/Builtin Extensions/Cython Magics.ipynb

@@ -27,7 +27,7 b''
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "IPtyhon has a `cythonmagic` extension that contains a number of magic functions for working with Cython code. This extension can be loaded using the `%load_ext` magic as follows:"
+      "IPython has a `cythonmagic` extension that contains a number of magic functions for working with Cython code. This extension can be loaded using the `%load_ext` magic as follows:"
      ]
     },
     {