feat(analysis/normed_space/linear_isometry): `symm_trans` (#11892)
feat(analysis/normed_space/linear_isometry): `symm_trans` (#11892)

Add a `simp` lemma `linear_isometry_equiv.symm_trans`, like
`coe_symm_trans` but without a coercion involved.  `coe_symm_trans`
can then be proved by `simp`, so stops being a `simp` lemma itself.







leanprover-community/mathlib,leanprover-community/mathlib