Bump sphinx-proof from 0.2.1 to 0.3.0 (#672)

Bumps [sphinx-proof](https://github.com/executablebooks/sphinx-proof) from 0.2.1 to 0.3.0.
- [Release notes](https://github.com/executablebooks/sphinx-proof/releases)
- [Changelog](https://github.com/executablebooks/sphinx-proof/blob/main/CHANGELOG.md)
- [Commits](executablebooks/sphinx-proof@v0.2.1...v0.3.0)

---
updated-dependencies:
- dependency-name: sphinx-proof
  dependency-version: 0.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

environment.yml

@@ -11,7 +11,7 @@ dependencies:
     - sphinx-tojupyter==0.3.1
     - sphinxext-rediraffe==0.3.0
     - sphinx-exercise==1.0.1
-    - sphinx-proof==0.2.1
+    - sphinx-proof==0.3.0
     - sphinxcontrib-youtube==1.4.1
     - sphinx-togglebutton==0.3.2
     - sphinx-reredirects==1.0.0