applets/brightness: don't skip switch on tab
The Night Light delegate has special handling to select the switch on tab, but this is done in the delegate's contentItem, rather than directly in the delegate. As a consequence, it only works if the contentItem has focus, not if the delegate itself has focus, which happens regularly.
Instead, put the handler in the delegate directly; if focus is on the RowLayout (or elsewhere generally in the contentItem), handling will fall back to the delegate (unless overridden) anyway so this is the only place where we really need it.
BUG: 500703 FIXED-IN: 6.3.3