sourcehut: disable IPv6 completely for tests

Signed-off-by: Christoph Heiss <[e-mail]>

nixos/tests/sourcehut.nix

···
     virtualisation.diskSize = 4 * 1024;
     virtualisation.memorySize = 2 * 1024;
     networking.domain = domain;
+    networking.enableIPv6 = false;
     networking.extraHosts = ''
       ${config.networking.primaryIPAddress} builds.${domain}
       ${config.networking.primaryIPAddress} git.${domain}