HistServ is a real service now, remove special casing

irc/nickname.go

@@ -18,7 +18,6 @@ import (
 var (
 	restrictedNicknames = []string{
 		"=scene=",  // used for rp commands
-		"HistServ", // used to play back JOIN, PART, etc. to legacy clients
 	}
 
 	restrictedCasefoldedNicks = make(map[string]bool)