P: GPU FAQ should mention Select Subject and Select Sky

The Lightroom Classic GPU FAQ needs to be updated to include Select Subject and Select Sky as one of the ways that LR uses the GPU:

https://helpx.adobe.com/lightroom-classic/kb/lightroom-gpu-faq.html

It should also mention the error message that occurs when a user has a very old graphics driver on Windows and tries to do Select Subject and Select Sky.