fix(CI): remove CI env var to fix the CI (#1704)

xref:
materialsproject/pymatgen#4243 (comment)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **Chores**
- Updated GitHub Actions workflow configuration with a minor environment
variable adjustment to support testing processes.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>

Author: njzjz

.github/workflows/test.yml

@@ -21,7 +21,10 @@ jobs:
     - name: Install dependencies
       run: uv pip install --system -e .[test]
     - name: Test
-      run: coverage run --source=./dpgen -m unittest -v && coverage report
+      run: |
+        # https://github.com/materialsproject/pymatgen/issues/4243#issuecomment-2573310051
+        unset CI
+        coverage run --source=./dpgen -m unittest -v && coverage report
     - uses: codecov/codecov-action@v5
       env:
         CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}