Fixed typo in code snippet of multiplying of Gaussians.

05_Kalman_Filters.ipynb

@@ -957,7 +957,7 @@
     "Kalman filters are supposed to be hard! But this is very short and straightforward. All we are doing is multiplying the Gaussian that reflects our belief of where the dog is with the new measurement. Perhaps this would be clearer if we used more specific names:\n",
     "\n",
     "    def update_dog(dog_pos, dog_variance, measurement, measurement_variance):\n",
-    "        return multiply(dog_pos, dog_sigma, measurement, measurement_variance)"
+    "        return multiply(dog_pos, dog_variance, measurement, measurement_variance)"
    ]
   },
   {