[PDB-tech] network facility data

[Matt Griswold]

We're doing one final consistency check for API tags / fields / etc,
and https://github.com/peeringdb/1to2/issues/29 came up, I'm in favor
of removing.

Without that, the only other information in that relation is local_asn,
which I'm also not sure anyone uses, so we can probably just drop that
whole table and link networks directly to facilities.

Does anyone have a use case for keeping any of it?