Ensure that `Nat.max` only `simpl`s if it does not result into a pattern match.

8 jobs for master in 8 minutes and 22 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #25465
fp
build-coq.8.7.0

00:02:40

passed #25464
fp
build-coq.8.7.1

00:02:49

passed #25463
fp
build-coq.8.7.2

00:02:45

passed #25462
fp-timing
build-coq.8.8.0

00:02:40

passed #25461
fp
build-coq.8.8.1

00:02:51

passed #25460
fp
build-coq.8.8.2

00:02:55

passed #25459
fp-timing
build-coq.8.9.0

00:03:11

passed #25458
fp
build-coq.dev

00:07:55