once operational credentials are implemented, node ID should be read from them

[todo]

connectedhomeip/src/app/server/Mdns.cpp

Lines 40 to 50 in 561376d

	// TODO: once operational credentials are implemented, node ID should be read from them
	if (!DeviceLayer::ConfigurationMgr().IsFullyProvisioned())
	{
	ChipLogError(Discovery, "Device not fully provisioned. Node ID unknown.");
	return chip::kTestDeviceNodeId;
	}
	// Admin pairings should have been persisted and should be loadable
	// TODO: once multi-admin is decided, figure out if a single node id
	// is sufficient or if we need multi-node-id advertisement. Existing

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This issue was generated by todo based on a TODO comment in 561376d when #5004 was merged. cc @andy31415.