If you got this notice and are not sure how to update your deprecated node.js runtime, hopefully this post will help.
The first step would be to goto your Google cloud functions. You can goto your Google console and search 'cloud functions'
This should list all the cloud functions that were created by FF, Integrated extensions, and your custom cloud functions you deployed.
Under the Runtime column, look for any warning nodes.js that might be between 10 and 16.
If the function is part of a Firebase integration, the best way to update this is to go back to Firebase > Extensions and see what extension you may be using. Any extension that shows an update is available, click on the update button and allow it to re-deploy those. This should likely update the cloud fn node.js to the latest version.
If you have deprecated nodes for functions like Stripe, Braintree, RevenueCat, etc. These are best fixed by going to FF > Settings > Stripe (or whichever one you're using) and click the green check button to re-deploy the credentials which should also update the node.js to the most up-to-date version.
Finally, if you have any remaining cloud functions that aren't listed above, you can manually update them in the Google Console > Cloud Functions. To do this, click on the function and goto SOURCE > EDIT. This will give you the option to change the Runtime to Node.js 18. Just click SAVE AND DEPLOY.
Hope this information helps.