[circt-test][verif] Un XFAIL two integration tests

[seldridge]

In 2b42ecb, two tests were marked XFAIL due to them seemingly having issues with empty verif.formal ops due to optimizations causing the removal of the only assertions defined in the verif.formal bodies. Specifically, things like assert(true) are now removed. However, the tooling seems to dislike this as it is a "nothing to prove" misconfiguration.

While sby was happy with a formulation of cover(true), circt-bmc seemed to not take this.

Get these tests re-enabled.

[fabianschuiki]

Thanks for opening up a tracking issue for this 🏅