Fix broken Flask-CORS link in docs

docs/examples/web_service.ipynb

@@ -225,7 +225,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Again, one thing to take into account is the security of running such a web server. However, apart from deploying the flask server in a secure and performant way, we also need one extra thing to circumvent a standard security feature of the browser. Without handling Cross Origin Resource Sharing (CORS) on the server, the JavaScript code on the client side will not be able to access the web service's reply. A Flask extension exists however, [Flask-CORS](https://flask-cors.readthedocs.io/), and we refer to its documentation for further details."
+    "Again, one thing to take into account is the security of running such a web server. However, apart from deploying the flask server in a secure and performant way, we also need one extra thing to circumvent a standard security feature of the browser. Without handling Cross Origin Resource Sharing (CORS) on the server, the JavaScript code on the client side will not be able to access the web service's reply. A Flask extension exists however, [Flask-CORS](https://flask-cors.corydolphin.com/), and we refer to its documentation for further details."
    ]
   },
   {