'Select a kernel' walkthrough step button does nothing

[joyceerhl]

Testing #8793

[minsa110]

Fixed per #8823

[roblourens]

The command doesn't work when I run it from the command palette here since the focus is not in the notebook editor

[roblourens]

I don't know if it's possible to do this with a button in the getting started page, since the command needs to run with the notebook focused. You probably just have to tell the user to click the Select Kernel button

[roblourens]

There's still a button on that page that doesn't work.

[roblourens]

We could probably have the command operate on whichever notebook editor is in the foreground (even if it's not focused). That sounds reasonable to me, tbh. I can look into that if you want to go that route.