Regenerate GitHub Actions workflow

Executed command: sbt githubWorkflowGenerate

Author: http4s-steward[bot]

.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
     timeout-minutes: 60
     steps:
       - name: Checkout current branch (full)
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0