Remove needless *_support_ntor()
While reviewing legacy/trac#7144 (moved), I noticed that circuit_cpath_supports_ntor() is pointless: We no longer allow TAP-only relays on the network, IIUC.
Assuming that I've got that right, we can rip out some code.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information