docs: announce the end of support

[bajtos]

Links:

• Spark: Sunset Graphsync retrievals roadmap#158
• Archive rusty-lassie and zinnia roadmap#278

[pyropy]

Will be missed 🙏🏻

[juliangruber]

🫡

[bajtos]

In order to trigger offline mode in Checker Desktop and show offline status icon in the tray menu, the error message has to start with the prefix Spark (the space character is important).

See https://github.com/CheckerNetwork/desktop/blob/14007f3e9b252b989624b90be7ecbd067b1c0df0/main/activities.js#L38-L39

I updated the message to the following:

Spark update: Filecoin Station and Checker Network programmes ended. The node is no longer contributing to the network, and there will be no further rewards. Thank you for your participation!