Results 1 issues of Jack Wang

Shouldn't the |bn-l| be |cn-l| in the last second line of [Sandwich Theorem](https://leanprover-community.github.io/format_lean/example/sandwich.html)? ![image](https://github.com/leanprover-community/mathlib4/assets/25180263/95a0289c-cbd4-44e7-bb36-abb532e972e9)