Remove redundant trace counter increment

The `incAndTraceMessageCount` is already called above
in this method.

This is a follow up of the change in ag/34027656
where I thought I removed this but I forgot to actually do that.

Flag: EXEMPT bugfix
Bug: 424307660
Test: PerfettoTraceMessageQueueTest
Change-Id: I8fab06c206df844b9a2ad4891b7d785281927106