Bump mamba-org/setup-micromamba from 1.8.1 to 1.9.0 (#361)

Bumps [mamba-org/setup-micromamba](https://github.com/mamba-org/setup-micromamba) from 1.8.1 to 1.9.0.
- [Release notes](https://github.com/mamba-org/setup-micromamba/releases)
- [Commits](mamba-org/setup-micromamba@v1.8.1...v1.9.0)

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

.github/workflows/docs.yml

@@ -50,7 +50,7 @@ jobs:
           tlmgr list --only-installed
 
       - name: 🐍 Install Conda environment
-        uses: mamba-org/setup-micromamba@v1.8.1
+        uses: mamba-org/setup-micromamba@v1.9.0
         with:
           environment-file: .github/workflows/micromamba/docs.yml
           environment-name: docs