fix some typos

<div id="comment:0"></div>

found using codespell or egrep

Component: **documentation**

Author: **Frédéric Chapoton**

Branch/Commit: **[`83e0322`](https://github.com/sagemath/sagetrac-mirror/commit/83e0322c3f81a5fc807480dae1c90d4d776984a9)**

Reviewer: **Sébastien Labbé**

_Issue created by migration from https://trac.sagemath.org/ticket/34613_

