fixup! Replace RelayMap::extend() member fn with RelayMap::join

Author: matthiasbeyer

iroh-relay/src/relay_map.rs

@@ -115,8 +115,6 @@ impl RelayMap {
     /// Joins this `RelayMap` with another one into a new one
     pub fn join(self, other: RelayMap) -> RelayMap {
         let mut a = self.relays.write().expect("poisoned");
-
-        // SAFETY: We have exclusive access to this object
         let b = other.relays.read().expect("poisoned");
         a.extend(b.iter().map(|(a, b)| (a.clone(), b.clone())));
     }