__upto_bind_eq_ssim is broken

[nchappe]

Since the generalization of ssim up-to-bind (f755434).

This is a non-trivial problem, as a ssim (update_val_rel eq eq) appears, which is not equivalent to just ssim eq because of the annoying type parameter in the val case.

The coffee machine example (more specifically the coffee_ssim proof) is a good starting point to take a closer look at the problem.