Bump sphinx-gallery from 0.17.1 to 0.18.0 in /requirements

Bumps [sphinx-gallery](https://github.com/sphinx-gallery/sphinx-gallery) from 0.17.1 to 0.18.0.
- [Release notes](https://github.com/sphinx-gallery/sphinx-gallery/releases)
- [Changelog](https://github.com/sphinx-gallery/sphinx-gallery/blob/master/.github_changelog_generator)
- [Commits](sphinx-gallery/sphinx-gallery@v0.17.1...v0.18.0)

---
updated-dependencies:
- dependency-name: sphinx-gallery
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -9,7 +9,7 @@ pytest-sphinx==0.6.3
 pyvista==0.44.1
 sphinx==7.1.0
 sphinx-copybutton==0.5.2
-sphinx-gallery==0.17.1
+sphinx-gallery==0.18.0
 sphinx-notfound-page==1.0.4
 sphinx-reredirects==0.1.3
 sphinx_design==0.6.1