Bump mamba-org/setup-micromamba from 1 to 2

Bumps [mamba-org/setup-micromamba](https://github.com/mamba-org/setup-micromamba) from 1 to 2.
- [Release notes](https://github.com/mamba-org/setup-micromamba/releases)
- [Commits](mamba-org/setup-micromamba@v1...v2)

---
updated-dependencies:
- dependency-name: mamba-org/setup-micromamba
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/tox-pytest.yml

@@ -20,7 +20,7 @@ jobs:
           fetch-depth: 2
 
       - name: Set up conda environment for testing
-        uses: mamba-org/setup-micromamba@v1
+        uses: mamba-org/setup-micromamba@v2
         with:
           environment-file: environment.yml
           cache-environment: true