Bump mamba-org/setup-micromamba from 1 to 2 in the actions group

Bumps the actions group with 1 update: [mamba-org/setup-micromamba](https://github.com/mamba-org/setup-micromamba).


Updates `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
  dependency-group: actions
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/tests.yml

@@ -99,7 +99,7 @@ jobs:
           sed -i '/dipy/d' environment.yml
           sed -i 's/- mne$/- mne-base/' environment.yml
         if: matrix.os == 'ubuntu-latest' && startswith(matrix.kind, 'conda') && matrix.python == '3.12'
-      - uses: mamba-org/setup-micromamba@v1
+      - uses: mamba-org/setup-micromamba@v2
         with:
           environment-file: ${{ env.CONDA_ENV }}
           environment-name: mne