Update and clarify doc strings

common/lib/xmodule/xmodule/capa_module.py

@@ -709,7 +709,7 @@ class CapaDescriptor(RawDescriptor):
 
     @property
     def editable_metadata_fields(self):
-        """Remove metadata from the editable fields since it has its own editor"""
+        """Remove any metadata from the editable fields which have their own editor or shouldn't be edited by user."""
         subset = [field for field in super(CapaDescriptor,self).editable_metadata_fields
                   if field not in ['markdown', 'empty']]
         return subset

common/lib/xmodule/xmodule/html_module.py

@@ -174,7 +174,7 @@ class HtmlDescriptor(XmlDescriptor, EditingDescriptor):
 
     @property
     def editable_metadata_fields(self):
-        """Remove metadata from the editable fields since it has its own editor"""
+        """Remove any metadata from the editable fields which have their own editor or shouldn't be edited by user."""
         subset = [field for field in super(HtmlDescriptor,self).editable_metadata_fields
                   if field not in ['empty']]
         return subset