add an unsupported feature

Author: michiya

sql_server/pyodbc/features.py

@@ -16,6 +16,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     ignores_quoted_identifier_case = True
     requires_literal_defaults = True
     requires_sqlparse_for_splitting = False
+    supports_index_on_text_field = False
     supports_nullable_unique_constraints = False
     supports_paramstyle_pyformat = False
     supports_partially_nullable_unique_constraints = False