thunderbird: set build timeout at eight hours

This matches a similar change made to Firefox in #96767.
A lot of code is shared between Firefox and Thunderbird
so it makes sense to increase timeouts for Thunderbird
as well.

pkgs/applications/networking/mailreaders/thunderbird/default.nix

@@ -332,5 +332,6 @@ stdenv.mkDerivation rec {
     ];
     platforms = platforms.linux;
     license = licenses.mpl20;
+    timeout = 28800; # eight hours
   };
 }