nixos/ollama: add network-online.target to ollama-model-loader.service (#443374)

nixos/modules/services/misc/ollama.nix

···
         "multi-user.target"
         "ollama.service"
       ];
-      after = [ "ollama.service" ];
+      wants = [ "network-online.target" ];
+      after = [
+        "ollama.service"
+        "network-online.target"
+      ];
       bindsTo = [ "ollama.service" ];
       environment = config.systemd.services.ollama.environment;
       serviceConfig = {