chore(algebra/lie/engel): speed up proof of Engel's theorem slightly (#12205)
chore(algebra/lie/engel): speed up proof of Engel's theorem slightly (#12205)

Local measurements using `set_option profiler true` are noisy but indicate
that this speeds up elaboration of `lie_algebra.is_engelian_of_is_noetherian`
by about 20% from about 10s to about 8s.







leanprover-community/mathlib,leanprover-community/mathlib