fix(category_theory/monoidal): improve hygiene in coherence tactic (#13507)
fix(category_theory/monoidal): improve hygiene in coherence tactic (#13507)




Co-authored-by: Scott Morrison <63f04b4d96235eb042cc46d94f14d241d2a26722@gmail.com>

leanprover-community/mathlib,leanprover-community/mathlib