Bump imageio from 2.30.0 to 2.31.0 in /requirements (#265)

Bumps [imageio](https://github.com/imageio/imageio) from 2.30.0 to 2.31.0.
- [Release notes](https://github.com/imageio/imageio/releases)
- [Changelog](https://github.com/imageio/imageio/blob/master/CHANGELOG.md)
- [Commits](imageio/imageio@v2.30.0...v2.31.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/requirements_docs.txt

@@ -1,6 +1,6 @@
 Sphinx<8
 ansys-sphinx-theme==0.9.9
-imageio==2.30.0
+imageio==2.31.0
 notfound==1.0.2
 pypandoc==1.11
 pyvista==0.39.1