build(deps): bump mamba-org/setup-micromamba 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 2 to 3
- [Release notes](https://github.com/mamba-org/setup-micromamba/releases)
- [Commits](mamba-org/setup-micromamba@v2...v3)

---
updated-dependencies:
- dependency-name: mamba-org/setup-micromamba
  dependency-version: '3'
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

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

Author: dependabot[bot]

.github/workflows/test-conda.yml

@@ -35,7 +35,7 @@ jobs:
       # Setup environment
       - uses: actions/checkout@v6
       - name: Create micromamba environment . . .
-        uses: mamba-org/setup-micromamba@v2
+        uses: mamba-org/setup-micromamba@v3
         with:
           environment-name: libsemigroups
           cache-environment: false