What would happen if you missed it, the lead shot has to go somewhere?
Note this is Russian development, by a defense contractor.
What happens to pellets, actually the same thing if you hit target. The shot pattern is wide enough that 80% of pellets would fall to earth. Yes, it will fall but the trajectory path isn't far before energy is consumed and pellets drop at gravity.
But on a different angle, I don't think if dispatching a Hunter Drone there would be a concern or focus on pellets, it'd be focused on stopping the target as in any aerial combat.
Here in USA we're probably the only country that hasn't conducted some form of combative maneuvers in peace time. The Russian airspace particularly will change from non-combative to combative, for that matter the Russian / Ukrainian streets will switch to combative in a blink too. Due to environments to react quickly, lengthy warnings have never been practiced much in-country.
Never the less, the pellets would fall to ground.
** Edited ** in reflection, we have had a few USA combative aerial missions but rarely released any ordnance. But in comparison to other countries, ours are practically non-existent. If you traveled into any soviet block country prior to fall of empire, you may not have known it or seen them, but you were being escorted in & out of airports with Migs.