Remove legacy disable triple buffering config

The config changes the dequeue limit of BQ (setMaxDequeuedBufferCount) from 2 to 1,  decreasing the default size of the queue from (3 to 2).
Some of the motivations behind this change include:
- not applicable in most scenarios since producers in the system override this
- breaks async mode, not well tested in other scenarios
- simplifying some of the implementation and removes a configuration/flag.

Clients can still manually call setMaxDequeuedBufferCount if they wish.

Test: presubmit
Fixes: 182314340
Change-Id: I724218d14ad106a4b7af69f7eacf97fae3c93923