Fixed #23106 -- Updated class-based view reference title.

docs/ref/class-based-views/index.txt

@@ -1,6 +1,6 @@
-=================
-Class-based views
-=================
+=====================
+Class-based views API
+=====================
 
 Class-based views API reference. For introductory material, see
 :doc:`/topics/class-based-views/index`.