build(deps): bump prefix-dev/setup-pixi from 0.8.3 to 0.8.4

Bumps [prefix-dev/setup-pixi](https://github.com/prefix-dev/setup-pixi) from 0.8.3 to 0.8.4.
- [Release notes](https://github.com/prefix-dev/setup-pixi/releases)
- [Commits](prefix-dev/setup-pixi@v0.8.3...v0.8.4)

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

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - uses: prefix-dev/[email protected].3
+      - uses: prefix-dev/[email protected].4
         with:
           cache: true
           frozen: true