gh-38100: Remove nitpick_patch_config function
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes #12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes #12345". -->
Fixes #37996.
We remove this function
```python
def nitpick_patch_config(app):
"""
Patch the default config for nitpicky
[...] ensure that nitpicky is not considered as a Sphinx
environment variable but rather as a Sage environment variable. As a
consequence, changing it doesn't force the recompilation of the
entire
documentation.
"""
app.config.values['nitpicky'] = (False, 'sage')
app.config.values['nitpick_ignore'] = ([], 'sage')
```
from `src/sage_docbuild/conf.py`.
The original purpose of the function seems to change `"env"` to `"sage"`
for `nitpicky` config variable. But the recent Sphinx is setting `""`
(empty string) instead of `"env"` by default. See
https://github.com/sphinx-doc/sphinx/blob/48cbb43e28efe82b198137042811e0
ade3599ae7/sphinx/config.py#L250C1-L250C41
- Hence the function is already no-op. But this old and obsolete
function is the cause of #37996. Hence we simply remove it.
- To prepare for Sphinx 7.3.7, we also remove some code which seems to
have become obsolete when `sage -clone` was removed long time ago.
- Made some docstring up-to-date, to test incremental doc build.
### :memo: Checklist
<!-- Put an `x` in all the boxes that apply. -->
- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [x] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
### :hourglass: Dependencies
<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - #12345: short description why this is a dependency -->
<!-- - #34567: ... -->
URL: https://github.com/sagemath/sage/pull/38100
Reported by: Kwankyu Lee
Reviewer(s):
