Fix release 0.38.0

Replace `@@plpythonu@@` vars in old_versions

server/extension/old_versions/cdb_dataservices_server--0.20.0--0.21.0.sql

@@ -62,7 +62,7 @@ RETURNS TABLE (
         raise Exception('Error trying to OBS_GetData')
     finally:
         quota_service.increment_total_service_use(len(geomvals))
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;
 
 CREATE OR REPLACE FUNCTION cdb_dataservices_server._OBS_GetData(
   username TEXT,
@@ -123,7 +123,7 @@ RETURNS TABLE (
         raise Exception('Error trying to OBS_GetData')
     finally:
         quota_service.increment_total_service_use(len(geomrefs))
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;
 
 CREATE OR REPLACE FUNCTION cdb_dataservices_server._OBS_GetMeta(
   username TEXT,
@@ -171,4 +171,4 @@ RETURNS JSON AS $$
         import sys
         logger.error('Error trying to OBS_GetMeta', sys.exc_info(), data={"username": username, "orgname": orgname})
         raise Exception('Error trying to OBS_GetMeta')
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;