build(deps): bump prefix-dev/setup-pixi from 0.7.0 to 0.8.1

Bumps [prefix-dev/setup-pixi](https://github.com/prefix-dev/setup-pixi) from 0.7.0 to 0.8.1.
- [Release notes](https://github.com/prefix-dev/setup-pixi/releases)
- [Commits](prefix-dev/setup-pixi@v0.7.0...v0.8.1)

---
updated-dependencies:
- dependency-name: prefix-dev/setup-pixi
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/tests.yaml

@@ -18,7 +18,7 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
-    - uses: prefix-dev/setup-pixi@v0.7.0
+    - uses: prefix-dev/setup-pixi@v0.8.1
       with:
           run-install: true
     - name: Post-install dependencies