Similar to allowing update of priorities when `priority_end` is greater than `priority_start`, to support inverted priority ranges, allow that change to propagate into `formatPriority` and display in the board view.
It's common to want an 'inverted' priority range, for example where P0 is the highest. The task helper logic would hide priority editing when priority_end was larger than priority_start. This logic change allows it by checking that priority_start and priority_end are different.
