Use mse instead of Brier score.

Author: MarkDaoust

site/en/tutorials/structured_data/imbalanced_data.ipynb

@@ -449,7 +449,7 @@
         "Good metrics to assess probabilistic predictions are, in fact, **proper scoring rules**. Their key property is that predicting the true probability is optimal. We give two well-known examples:\n",
         "\n",
         "*   **cross entropy** also known as log loss\n",
-        "*   **Brier score** also known as squared error\n",
+        "*   **Mean squared error** also known as the Brier score\n",
         "\n",
         "#### Metrics for deterministic 0/1 predictions\n",
         "\n",