vestigial cfg gate in receive/v1/mod.rs #1917

Unrelated to this PR but this seems odd.. Why is this "not v1" feature gate here in the v1 module??

Originally posted by @spacebear21 in #1446 (comment)

This should be removed because it should be switched off entirely if not(v1) now switched on at receive/mod.rs. I guess this is vestigial from when there was no common and v2 wrapped v1. If you agree with my design, please PR it's removal as follow-up @xstoicunicornx