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/ci.yml

@@ -35,7 +35,7 @@ jobs:
       uses: actions/checkout@v4
 
     - name: Set up conda environment
-      uses: mamba-org/setup-micromamba@v1
+      uses: mamba-org/setup-micromamba@v2
       with:
         environment-file: devtools/conda-envs/test_env.yaml
         create-args: >- # beware the >- instead of |, we don't split on newlines but on spaces