Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
 
       - uses: prefix-dev/setup-pixi@1b2de7f3351f171c8b4dfeb558c639cb58ed4ec0 # v0.9.5
         with: