Bump the github-actions group with 3 updates (PyPSA#156)

Bumps the github-actions group with 3 updates: [actions/checkout](https://github.com/actions/checkout), [mamba-org/setup-micromamba](https://github.com/mamba-org/setup-micromamba) and [actions/upload-artifact](https://github.com/actions/upload-artifact).


Updates `actions/checkout` from 2 to 4
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v4)

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)

Updates `actions/upload-artifact` from 3 to 4
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](actions/upload-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
- dependency-name: mamba-org/setup-micromamba
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
- dependency-name: actions/upload-artifact
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: github-actions
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yaml

@@ -6,8 +6,8 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
-    - uses: mamba-org/setup-micromamba@v1
+    - uses: actions/checkout@v4
+    - uses: mamba-org/setup-micromamba@v2
       with:
         micromamba-version: latest
         environment-file: environment.yaml
@@ -20,7 +20,7 @@ jobs:
       run: |
         snakemake --cores all -f compile_cost_assumptions
     - name: Upload artifacts
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: technology-data
         path: outputs/