Fix duplicate deps issue related to stubs

It turns out that we accidentally add deps twice to the apex related
config axes if they exist simultaneously in the android and
no-config axes in the bp2build logic for stubs. This change ensures
that this does not happen.

Fixes: 245518215
Test: Unit tests
Test: bp2build with relevant module
Change-Id: Iab037d60a08a869f6ee00928090d2b544490590b