Remove all equal deflates.

Currently we only check the src and dst deflates that have the same
index, this patch uses the new puffin::RemoveEqualBitExtent() to
remove all the equal ones.

This actually reduced payload size slightly probably because the
puffin protobuf is smaller or the puffed stream is smaller.

Bug: None
Test: generate a delta payload
Change-Id: Ia4559e091fdfac8785554a7869545137db22c3fb