Tasks: Do not select Go back by default, isolate it from the other options

[joaomoreno]

Testing #93746 on Linux

1. Open a folder with package.json
2. Tasks: Run Task
3. Pick npm

🐛 Go back should be separated from the rest using a separator. It should also probably not be the option selected by default.

[alexr00]

Added a separator and moved to the end.

[Tyriar]

@alexr00 up the top might still be good as it aligns with the simple file picker, just have the second item selected? Open recent does this as the most recently opened window is the current window.