Allow the gitlab-deps server to restart on error without limits

Should let gitlab-deps handle temporary unavailability of Gitlab on
startup, by simply retrying until the server comes back. The increased
RestartSec ensures we're not overwhelming the host with restarts.

debian/gitlab-deps.service

 [Unit]
 Description=gitlab-deps server
 After=network.target
+StartLimitIntervalSec=0
 
 [Service]
 Type=simple
 Restart=on-failure
+RestartSec=3
 EnvironmentFile=/etc/default/gitlab-deps
 ExecStart=/usr/sbin/gitlab-deps-server-wrapper
 User=gitlab-deps