aconfig: OWNERS: mark amhk, joeo, jham as LAST_RESORT_SUGGESTION

Mark the aconfig owners that are not actively working on the project as
LAST_RESORT_SUGGESTION to make this fact more clear to everyone.

Bug: none
Test: none
Change-Id: Ide49ec3a48fdc51d046e9b9f25b43facb7b0e83e