bird: 2.0.12 -> 2.13

Change in versioning scheme from `<epoch>.<major>.<minor>` to
`<major>.<minor>.<patch>`. Also

- Babel: IPv4 via IPv6 extension (RFC 9229)
- Babel: Improve authentication on lossy networks
- BGP: New 'allow bgp_med' option
- BSD: Support for IPv4 routes with IPv6 nexthop on FreeBSD
- Experimental BMP protocol implementation
- Important bugfixes

Source and release notes:
<https://bird.network.cz/pipermail/bird-users/2023-April/016863.html>

pkgs/servers/bird/default.nix

@@ -2,11 +2,11 @@
 
 stdenv.mkDerivation rec {
   pname = "bird";
-  version = "2.0.12";
+  version = "2.13";
 
   src = fetchurl {
     url = "ftp://bird.network.cz/pub/bird/${pname}-${version}.tar.gz";
-    hash = "sha256-PsRiojfQbR9EVdbsAKQvCxaGBh/JiOXImoQdAd11O1M=";
+    hash = "sha256-jYlePjEYgOnvuIi0OGy+wvfhi/uDNOjUyMp8Q0EJJjg=";
   };
 
   nativeBuildInputs = [ flex bison ];