Update netbox.md
Update netbox.md

Added libpq-dev as a dependency so the pip install of requirements.txt will complete.
Alphalink/netbox,Alphalink/netbox,digitalocean/netbox,snazy2000/netbox,rfdrake/netbox,digitalocean/netbox,lampwins/netbox,lampwins/netbox,snazy2000/netbox,Alphalink/netbox,snazy2000/netbox,rfdrake/netbox,Alphalink/netbox,snazy2000/netbox,digitalocean/netbox,lampwins/netbox,lampwins/netbox,rfdrake/netbox,digitalocean/netbox,rfdrake/netbox