Update actions/checkout action to v7 (#209)

Co-authored-by: dependencyupdates[bot] <218638057+dependencyupdates[bot]@users.noreply.github.com>

Author: dependencyupdates[bot]

.github/workflows/ci.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v6.0.3
+        uses: actions/checkout@v7.0.0
         with:
           fetch-depth: 0
           submodules: true