Remove propagated literals when removing a PB constraint
It may happen in some cases that a PB constraint propagates literals at decision zero. In case of clauses or cardinality constraints, a unit clause of a set of unit clauses are returned, so when those constraints are removed, they are removed from the trail.
In the case of PB constraints, the propagated literals are not associated to unit clauses. As such, the remove method in PB constraint should take care to remove from the trail the implied literals (the ones pushed at decision level 0).
The issue was discovered by Yacoub in the context of maxsat solving using lower bounding.