Unconstrain conditional offers w.r.t. name uniqueness

[matthugs]

Unclear why oscar is opinionated about this, and given our setup processes for these when they're attached to programs it doesn't make a lot of sense to enforce this.

Potential downsides: Oscar says that it shows these names in the learner's cart when the offer applies. I have not investigated that, but it's possible this could lead to confusing end-user experiences in truly pathological situations where multiple offers have exactly the same (or extremely similar names), if we present them to the user in that way.