client/web: use IPv4 instead of IP in login view (#10483)

The IP property in node data was renamed to IPv4 but refactoring the usage
of the property was missed in this file.

Updates https://github.com/tailscale/tailscale/issues/10261

Signed-off-by: Mario Minardi <mario@tailscale.com>

client/web/src/components/views/login-view.tsx

@@ -49,7 +49,7 @@ export default function LoginView({
             Connect to Tailscale
           </Button>
         </>
-      ) : data.IP ? (
+      ) : data.IPv4 ? (
         <>
           <div className="mb-6">
             <p className="text-gray-700">