Improve image of loss functions shape

Change-Id: Id226323a736038fb3c9b9009448e5ece12dc63ee
diff --git a/docs/source/loss.png b/docs/source/loss.png
index 9f98d00..5c9ac07 100644
--- a/docs/source/loss.png
+++ b/docs/source/loss.png
Binary files differ