remove attributes that were not generated automatically (no docstring page to link to)

Author: jorisvandenbossche

doc/source/reference/index.rst

@@ -50,7 +50,6 @@ public functions related to data types in pandas.
         api/pandas.DataFrame.blocks
         api/pandas.DataFrame.as_matrix
         api/pandas.DataFrame.ix
-        api/pandas.Index.asi8
         api/pandas.Index.data
         api/pandas.Index.flags
         api/pandas.Index.holds_integer
@@ -63,12 +62,3 @@ public functions related to data types in pandas.
         api/pandas.Series.ix
         api/pandas.Series.imag
         api/pandas.Series.real
-
-
-.. Can't convince sphinx to generate toctree for this class attribute.
-.. So we do it manually to avoid a warning
-
-..
-    .. toctree::
-
-        api/pandas.api.extensions.ExtensionDtype.na_value