Adapt to stdpp!566
Latest stdpp had a merge request (stdpp!566 (merged)) that upstreamed (and further improved upon) the more fancy gmap induction scheme originally written down here: https://gitlab.mpi-sws.org/iris/simuliris/-/blob/master/theories/tree_borrows/steps_wf.v?ref_type=heads#L63
That script also defines an ad-hoc tactic for doing induction on such maps that really ought to be replaced by something less ad-hoc. This should be possible, once a version of stdpp with that merge included becomes available.
