Update triggering to not double trigger at severe threshold

If the low threshold is not shown for any reason and we reach the
severe threshold and it does show it will double trigger. This CL
just makes it so both are marked as "shown" if the severe warning
is shown regardless of whether the low warning was shown or not.

Test: runtest systemui
Bug: 116716293
Change-Id: I7fff2d7beba7b37312b9a4c4951a68c3d1f1ba3f