Require client protocol versions based on 0.3.5.7
Assuming legacy/trac#32696 (moved) is deployed between March and June 2020, we should make the 0.3.5.7 protocol versions required for clients some time in 2021.
See: https://gitweb.torproject.org/torspec.git/tree/proposals/303-protover-removal-policy.txt#n49