fix(*): remove `@[nolint simp_nf]` (#2450)
This removes a couple more nolints:
- `coe_units_equiv_ne_zero` doesn't cause any problems anymore
- `coe_mk` is redundant
- `mk_eq_div` was not in simp-normal form (previously the linter timed out instead of reporting it as an error)
- `factor_set.coe_add` is redundant
