Fix order of index columns

drivers/spanner/spanner.go

@@ -170,7 +170,7 @@ SELECT
    SELECT COLUMN_NAME
    FROM INFORMATION_SCHEMA.INDEX_COLUMNS
    WHERE TABLE_NAME = c.TABLE_NAME AND INDEX_NAME = c.INDEX_NAME AND INDEX_TYPE = c.INDEX_TYPE AND COLUMN_ORDERING IS NOT NULL
-   ORDER BY COLUMN_ORDERING ASC
+   ORDER BY ORDINAL_POSITION ASC
  ), ", ") AS columns,
  ARRAY_TO_STRING(ARRAY(
    SELECT COLUMN_NAME