chore: Bump actions/checkout from 4 to 6 (#612)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Valérian Rey <31951177+ValerianRey@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/checks.yml

@@ -89,7 +89,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       # This will restore the cache for the current commit if it exists, or the most recent lychee
       # cache otherwise (including those saved for the main branch). It will also save the cache for