remove removed specificchain from classes doc

Author: wholmgren

docs/sphinx/source/classes.rst

@@ -24,20 +24,13 @@ PVSystem
     :members:
     :undoc-members:
     :show-inheritance:
-    
+
 ModelChain
 ----------
 .. autoclass:: pvlib.modelchain.ModelChain
     :members:
     :undoc-members:
     :show-inheritance:
-    
-MoreSpecificModelChain
-----------------------
-.. autoclass:: pvlib.modelchain.MoreSpecificModelChain
-    :members:
-    :undoc-members:
-    :show-inheritance:
 
 LocalizedPVSystem
 -----------------