Implement suggestions by Robbert Krebbers on list’s lemmas.

Status Job ID Name Coverage
  Build
canceled #39347
fp
build-coq.8.10.dev

canceled #39353
fp
build-coq.8.7.2

canceled #39352
fp-timing
build-coq.8.8.0

canceled #39351
fp
build-coq.8.8.1

canceled #39350
fp
build-coq.8.8.2

canceled #39349
fp-timing
build-coq.8.9.0

canceled #39348
fp
build-coq.8.9.1

canceled #39346
fp
build-coq.dev