Regenerate GitHub Actions workflow

Executed command: sbt githubWorkflowGenerate

Author: scala-steward

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0