feat(measurable_space): is_measurable_supr lemma (#2092)
* feat(data/set/lattice): add @[simp] to lemmas
* feat(measurable_space): is_measurable_supr lemma
* fix proof
* fix proof
* fix proof
* oops
* fix proofs
* typo in doc string
* remove @[simp]
Co-authored-by: sgouezel <sebastien.gouezel@univ-rennes1.fr>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
