[entropy panel] re-enable mousewheel zooming

[jameshadfield]

#1684 notes:

Mousewheel zooming has been disabled. I should bring it back, but it needs a proper debounce.

The code is still there, but the function's not called. It would be good to bring back as we support the same concept in the map. For me (using an Apple Magic Mouse) the zoom resulted in a number of events being queued up which essentially froze auspice for some time.