applets/taskmanager: don't time out preview tooltips
In general we don't time out any tooltips now as long as the cursor remains hovered over the thing that opened the tooltip. One exception is Task Manager window thumbnail tooltips. This may simply have been missed during the change to no longer time out any tooltips (it has a local override for the new default behavior) or it might have been intentional at the time. But either way, it's probably better to follow the default settings here for reasons of consistency, not to mention to make it easier to interact with the preview thumbnails, especially when there are multiple windows open.
BUG: 470043 FIXED-IN: 5.27.6