Remove imports from sage.rings.all in sage.schemes

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Part of Meta-ticket #34201.

CC:  @nbruin

Component: **refactoring**

Author: **Matthias Koeppe**

Branch/Commit: **[`cc5d6da`](https://github.com/sagemath/sagetrac-mirror/commit/cc5d6daf5843735baa87f6bedf8011eafa1737a3)**

Reviewer: **Kwankyu Lee**

_Issue created by migration from https://trac.sagemath.org/ticket/34190_

