Update dependencies

Update Iris. In particular, account for breaking changes in iris!461 (merged).

Btw, for reasons that I don't understand there are a few of the examples that I can't build. For instance, I get the error:

File "./theories/logatom/snapshot/atomic_snapshot.v", line 76, characters 35-43:
Error: Unbound value agreeR

This is not new and none of the files that error for me seems to be affected by this update.