nixos/tests/networking: fix GRE test (#360349)

Author: rnhmjoj

nixos/tests/networking/networkd-and-scripted.nix

@@ -462,6 +462,7 @@ let
               };
               bridges.bridge.interfaces = [ "greTunnel" "eth1" ];
               interfaces.eth1.ipv4.addresses = lib.mkOverride 0 [];
+              interfaces.eth1.ipv6.addresses = lib.mkOverride 0 [];
               interfaces.bridge.ipv4.addresses = lib.mkOverride 0 [
                 { address = "192.168.1.1"; prefixLength = 24; }
               ];
@@ -498,6 +499,7 @@ let
               };
               bridges.bridge.interfaces = [ "greTunnel" "eth2" ];
               interfaces.eth2.ipv4.addresses = lib.mkOverride 0 [];
+              interfaces.eth2.ipv6.addresses = lib.mkOverride 0 [];
               interfaces.bridge.ipv4.addresses = lib.mkOverride 0 [
                 { address = "192.168.1.2"; prefixLength = 24; }
               ];