mathlib3

e836a722 - feat(order/galois_connection): add `exists_eq_{l,u}`, tidy up lemmas (#9904)

feat(order/galois_connection): add `exists_eq_{l,u}`, tidy up lemmas (#9904) This makes some arguments implicit to `compose` as these are inferrable from the other arguments, and changes `u_l_u_eq_u` and `l_u_l_eq_l` to be applied rather than unapplied, which shortens both the proof and the places where the lemma is used.