mathlib

d9e96a3e - feat(data/list/dedup): Lemmas about `list.dedup` (#19142)

feat(data/list/dedup): Lemmas about `list.dedup` (#19142) Basic lemmas about `dedup` applied with `cons`, `nil`, `head`, and `tail`. Co-authored-by: Devon Tuma <devontuma@pop-os.localdomain>