aurweb: Double fd limit to avoid "Too many open files"

From time to time aurweb is failing with "Too many open files"
errors[1], this could indicate a bug in aurweb or perhaps the limit is
just too low. Let's try doubling the limit and see if it helps.

[1] https://gitlab.archlinux.org/archlinux/aurweb-errors/-/issues/275

roles/aurweb/templates/aurweb.service.j2

@@ -6,6 +6,7 @@ RuntimeDirectory={{ aurweb_prom_dir }}
 Environment=PROMETHEUS_MULTIPROC_DIR=/run/{{ aurweb_prom_dir }}
 User={{ aurweb_user }}
 WorkingDirectory={{ aurweb_dir }}
+LimitNOFILE=2048
 ExecStart=/usr/bin/poetry run gunicorn \
     --log-config {{ aurweb_dir }}/logging.conf \
     --bind {{ aurweb_asgi_bind }} \