nixos/journaldriver: import module in top-level module list

Imports the `journaldriver` module into the top-level NixOS module
list to make it usable without extra work.

This went unnoticed in #42134 (mostly because my setup imports modules
explicitly from pinned versions).

Fixes #50390

nixos/modules/module-list.nix

@@ -303,6 +303,7 @@
   ./services/logging/graylog.nix
   ./services/logging/heartbeat.nix
   ./services/logging/journalbeat.nix
+  ./services/logging/journaldriver.nix
   ./services/logging/journalwatch.nix
   ./services/logging/klogd.nix
   ./services/logging/logcheck.nix