Displays mismatched modlist with server when this mod is client only

Fixed in the latest releases for 1.16.5 and 1.17.1

@ichttt You are missing the DISPLAYTEST extension point in the mod constructor:

ModLoadingContext.get().registerExtensionPoint(
    ExtensionPoint.DISPLAYTEST,
    () -> Pair.of(() -> FMLNetworkConstants.IGNORESERVERONLY, (a, b) -> true)
);

God dammit, right