Fix "Gaussins" typo

Fixes rlabbe#493

03-Gaussians.ipynb

@@ -1381,7 +1381,7 @@
    "source": [
     "## Putting it all Together\n",
     "\n",
-    "Now we are ready to talk about how Gaussians can be used in filtering. In the next chapter we will implement a filter using Gaussins. Here I will explain why we would want to use Gaussians.\n",
+    "Now we are ready to talk about how Gaussians can be used in filtering. In the next chapter we will implement a filter using Gaussians. Here I will explain why we would want to use Gaussians.\n",
     "\n",
     "In the previous chapter we represented probability distributions with an array. We performed the update computation by computing the element-wise product of that distribution with another distribution representing the likelihood of the measurement at each point, like so:"
    ]