Bump mamba-org/setup-micromamba from 1.7.3 to 1.8.0 (#2)

Bumps [mamba-org/setup-micromamba](https://github.com/mamba-org/setup-micromamba) from 1.7.3 to 1.8.0.
- [Release notes](https://github.com/mamba-org/setup-micromamba/releases)
- [Commits](mamba-org/setup-micromamba@e820223...8767fb7)

---
updated-dependencies:
- dependency-name: mamba-org/setup-micromamba
  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>

.github/workflows/sphinx-to-gh-pages.yaml

@@ -23,7 +23,7 @@ jobs:
           fetch-depth: 0
 
       - name: Set up Conda environment with Micromamba
-        uses: mamba-org/setup-micromamba@e820223f89c8720d6c740ca154a7adf32fcd278a
+        uses: mamba-org/setup-micromamba@8767fb704bd78032e9392f0386bf46950bdd1194
         with:
            environment-file: envs/environment-gh-pages.yaml
            environment-name: numeric-gh-pages