ci: remove deprecated submodule code (#20731)

.github/workflows/submodule-sync.yml

@@ -1,21 +0,0 @@
-name: Submodule Sync
-on:
-  schedule:
-    # Runs "At minute 15 past every 4th hour." (see https://crontab.guru)
-    - cron: "15 */4 * * *"
-  workflow_dispatch: ~
-jobs:
-  submodule-sync:
-    name: Submodule update
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout Code
-        uses: actions/checkout@v4
-        with:
-          submodules: recursive
-          token: ${{ secrets.GH_ACCESS_TOKEN }}
-      - name: Commit
-        run: |
-          git config user.email "actions@github.com"
-          git config user.name "github-actions"
-          git commit -am "Auto updated submodule references" && git push || echo "No changes to commit"