Use the --no-comments option to pg_dump

Hopefully this will help with the pg_restore in the create-small-backup
script:

  pg_restore: [archiver (db)] Error while PROCESSING TOC:
  pg_restore: [archiver (db)] Error from TOC entry 2875; 0 0 COMMENT EXTENSION plpgsql
  pg_restore: [archiver (db)] could not execute query: ERROR:  must be owner of extension plpgsql
      Command was: COMMENT ON EXTENSION plpgsql IS 'PL/pgSQL procedural language';

scripts/guix-data-service-backup-database

@@ -16,6 +16,7 @@ renice 19 -p $$ || true
 ionice -p $$ -c 3 || true
 
 pg_dump --format=custom --compress=9 --serializable-deferrable \
+        --no-comments \
         --username=guix_data_service \
         --file="$TEMPORARY_FILE_NAME" \
         "$DATABASE_NAME"