remove deprecated stuff in manifolds

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

after #18783 and #19209

CC:  @egourgoulhon

Component: **geometry**

Author: **Frédéric Chapoton**

Branch/Commit: **[`52217e8`](https://github.com/sagemath/sagetrac-mirror/commit/52217e8dd1d044f7009fe50dbb18d80d1501763b)**

Reviewer: **Eric Gourgoulhon**

_Issue created by migration from https://trac.sagemath.org/ticket/26609_

