dashboard: fix showing showProgressDetails on md and up (#2760)
The DOM changed to accomodate RTL scripts, but this CSS rule was not
changed accordingly.
The StatusBar does not know its own width, so a standalone StatusBar
would never have an `.uppy-size--md` parent element. You only get that
with the Dashboard. So I've moved the rule to the Dashboard plugin, and
the selector now checks for `.uppy-Dashboard`. That element also has the
size classes.
The standalone StatusBar does not auto-hide progress details on narrow
screens. I think that's probably fine, if you're using it directly and
explicitly asking for progress details you might want to always see
them…