Verizon blocking moria1 directory authority by IP address

[Breaking this ticket out of #90 so we can focus on fixing just this part of it]

If you try to reach moria1's IP address from Verizon FIOS, it is filtered at an early hop:

$ traceroute 128.31.0.39
traceroute to 128.31.0.39 (128.31.0.39), 30 hops max, 60 byte packets
 1  Fios_Quantum_Gateway.fios-router.home (192.168.1.1)  1.552 ms  3.032 ms  2.973 ms
 2  lo0-100.NYCMNY-VFTTP-313.verizon-gni.net (100.37.95.1)  6.755 ms  7.153 ms  6.653 ms
 3  * * *
 4  * * *
 5  * * *
 6  * * *
 7  * * *
 8  *^C

whereas reaching the same destination computer by an alternate IP address works smoothly:

$ traceroute 128.31.0.24
traceroute to 128.31.0.24 (128.31.0.24), 30 hops max, 60 byte packets
 1  Fios_Quantum_Gateway.fios-router.home (192.168.1.1)  4.353 ms  4.162 ms  5.277 ms
 2  lo0-100.NYCMNY-VFTTP-313.verizon-gni.net (100.37.95.1)  8.972 ms  8.335 ms  8.500 ms
 3  G103-0-0-24.NYCMNY-LCR-22.verizon-gni.net (100.41.221.78)  13.079 ms G103-0-0-3.NYCMNY-LCR-21.verizon-gni.net (100.41.221.88)  14.615 ms G103-0-0-24.NYCMNY-LCR-22.verizon-gni.net (100.41.221.78)  12.467 ms
 4  * * *
 5  * * *
 6  * * *
 7  MASSACHUSET.ear2.Boston1.Level3.net (4.16.14.70)  9.962 ms  13.668 ms  13.809 ms
 8  dmz-rtr-2-external-rtr-1.mit.edu (18.0.162.17)  13.094 ms  13.825 ms  12.803 ms
 9  mitnet.core-1-ext.csail.mit.edu (18.0.162.142)  12.162 ms  11.541 ms  11.223 ms
10  moria.csail.mit.edu (128.31.0.24)  13.774 ms  13.429 ms  13.217 ms

I believe this block went into place around January 2021, during the attack on the Tor network where the attacker sent many directory requests to the dir auths via the Tor network. Maybe the Verizon folks saw the Tor relays running on the Verizon network sending lots of requests toward 128.31.0.39 and decided to make the traffic stop by nullrouting it.