Devourer doesn't stack on assists without an auto-attack

Steps to reproduce:

1. on a jungling champion, build smite and a devourer enchantment item
2. Start a jungling camp by smiting or using an ability
3. do not auto-attack the camp
4. have a teammate kill the camp

Expected result: Gain devourer stacks appropriate to the camp

Observed result: No stacks are gained

In a recent test game, it appeared that the above steps would reproduce the issue 100% of the time. Clearing a camp only counted as a takedown/assist if you auto-attack it.