add consistent SPDX copyright headers

lib-sql/partition-tables.src.sql

@@ -1,3 +1,10 @@
+-- SPDX-License-Identifier: GPL-2.0-only
+--
+-- This file is part of Nominatim. (https://nominatim.org)
+--
+-- Copyright (C) 2022 by the Nominatim developer community.
+-- For a full list of authors see the git log.
+
 drop table IF EXISTS search_name_blank CASCADE;
 CREATE TABLE search_name_blank (
   place_id BIGINT,