Update qualtran dependency to v0.6

[sammorley-short]

Qualtran v0.6 was recently released, but pyliqtr is currently pinned at v0.4.

Can this be updated so that it's compatible with the new features and dependencies, please? Thanks!

[kjm538]

This is a heavy lift for us as there are backwards incompatible changes that affect a lot of our functionality. We haven't updated to qualtran v0.5 yet for the same reason, although we have discussed it at length. Are there particular features/dependencies you're looking to use?

[sammorley-short]

There are various improvements in the newest versions of qualtran, but most notably from our side v0.5 introduces bartiq and QREF interoperability, which would make pyliqtr QREs interoperable with other QRE stacks.