bird2: fetch src url via https

pkgs/by-name/bi/bird2/package.nix

···
   version = "2.16.1";
 
   src = fetchurl {
-    url = "ftp://bird.network.cz/pub/bird/${pname}-${version}.tar.gz";
+    url = "https://bird.network.cz/download/bird-${version}.tar.gz";
     hash = "sha256-9uWcvMrKYmaK6gIGhyS9QnuexEnH4PD8VoFQOYjHNbQ=";
   };
 
···
   meta = with lib; {
     changelog = "https://gitlab.nic.cz/labs/bird/-/blob/v${version}/NEWS";
     description = "BIRD Internet Routing Daemon";
-    homepage = "http://bird.network.cz";
+    homepage = "https://bird.network.cz";
     license = licenses.gpl2Plus;
     maintainers = with maintainers; [ herbetom ];
     platforms = platforms.linux;