Fix release 0.38.0

Replace `@@plpythonu@@` vars in old_versions

server/extension/old_versions/cdb_dataservices_server--0.7.2--0.7.3.sql

@@ -12,7 +12,7 @@ RETURNS text AS $$
   user_obs_snapshot_config = GD["user_obs_snapshot_config_{0}".format(username)]
 
   return user_obs_snapshot_config.connection_str
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;
 
 CREATE OR REPLACE FUNCTION cdb_dataservices_server._OBS_GetDemographicSnapshot(
   username TEXT,
@@ -62,7 +62,7 @@ RETURNS json AS $$
       plpy.error(error_msg)
   finally:
       quota_service.increment_total_service_use()
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;
 
 CREATE OR REPLACE FUNCTION cdb_dataservices_server._OBS_GetSegmentSnapshot(
   username TEXT,
@@ -110,4 +110,4 @@ RETURNS json AS $$
       plpy.error(error_msg)
   finally:
       quota_service.increment_total_service_use()
-$$ LANGUAGE plpythonu;
+$$ LANGUAGE @@plpythonu@@;