manifest: use Lineage fork of external/tremolo

The July ASB contains a fix in external/tremolo. We already have
a fork of this repo, but we currently track AOSP. There is one commit
missing in comparison to 6.0.1_r79, which will be pushed. Afterwards,
the July ASB change can be merged.

Change-Id: Ibf9fd3fd46b85c29afd796b743c38d415c7935de