fit quiz in and use final structure

Author: burtenshaw

chapters/en/_toctree.yml

@@ -62,9 +62,9 @@
   - local: chapter3/4
     title: A full training loop
   - local: chapter3/5
-    title: Fine-tuning, Check!
-  - local: chapter3/6
     title: Understanding Learning Curves
+  - local: chapter3/6
+    title: Fine-tuning, Check!
   - local: chapter3/7
     title: End-of-chapter quiz
     quiz: 3