Bump imageio-ffmpeg from 0.4.7 to 0.5.1

Bumps [imageio-ffmpeg](https://github.com/imageio/imageio-ffmpeg) from 0.4.7 to 0.5.1.
- [Release notes](https://github.com/imageio/imageio-ffmpeg/releases)
- [Commits](imageio/imageio-ffmpeg@v0.4.7...v0.5.1)

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

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

requirements/requirements_docs.txt

@@ -1,7 +1,7 @@
 pypandoc==1.13
 imageio==2.34.0
 numpydoc==1.6.0
-imageio-ffmpeg==0.4.7
+imageio-ffmpeg==0.5.1
 Sphinx<7.2.0; python_version == '3.8'
 Sphinx==7.2.6; python_version >= '3.9'
 sphinx-autobuild==2024.4.16