build(deps): bump conda-incubator/setup-miniconda from 2 to 3

Bumps [conda-incubator/setup-miniconda](https://github.com/conda-incubator/setup-miniconda) from 2 to 3.
- [Release notes](https://github.com/conda-incubator/setup-miniconda/releases)
- [Changelog](https://github.com/conda-incubator/setup-miniconda/blob/main/CHANGELOG.md)
- [Commits](conda-incubator/setup-miniconda@v2...v3)

---
updated-dependencies:
- dependency-name: conda-incubator/setup-miniconda
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/unittests.yml

@@ -89,7 +89,7 @@ jobs:
         git config --global user.name 'NiPreps Bot'
         git config --global user.email '[email protected]'
     - name: Set up Python ${{ matrix.python-version }}
-      uses: conda-incubator/setup-miniconda@v2
+      uses: conda-incubator/setup-miniconda@v3
       with:
         auto-update-conda: true
         auto-activate-base: true