Disable "Launch as admin" combobox for apps that couldn't be launched elevated

[SeraphimaZykova]

Adding this issue for visibility.
Some apps, such as Settings, can't be launched as admin. To avoid launching errors, it'd be better to disable the combo box.

[SeraphimaZykova]

@plante-msft, does it sound good?

[plante-msft]

yes this sounds good - any confusion from users as to why it's greyed out can be covered in documentation. Thanks!