fix: only NPCs drop items when overencumbered

[OrenAudeles]

Summary

SUMMARY: Bugfixes "Only NPCs should be dropping items automatically when overencumbered"

Purpose of change

Fixes issue with the speed test errors mentioned by Olanti here

Only NPCs should be dropping items automatically when overencumbered. The player should not. The player can continue to just tumble items out if over volume capacity like they have been for a long time.

Describe the solution

Add an early out of the function if Character is not an NPC.

Describe alternatives you've considered

Leave the player automatically dropping items, modify test to add a fake activity target. That wouldn't have actually fixed the issue though.

Testing

Compiled, ran relevant tests, they passed.

Additional context

I need to be more on the ball about running the test suite for regressions.