ci: remove unmaintained upgrade-go workflow (#2104)

.github/workflows/upgrade-go.yaml

@@ -1,24 +0,0 @@
-name: Upgrade Go Version
-
-on:
-  # Run manually when needed
-  workflow_dispatch:
-  # Run weekly on Mondays at 8am UTC
-  schedule:
-    - cron: "0 8 * * MON"
-
-jobs:
-  upgrade-go:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: write
-      pull-requests: write
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v7
-
-      - name: Check for Go updates
-        uses: StefMa/Upgrade-Go-Action@v1
-        with:
-          base-branch: 'main'
-          gh-token: ${{ secrets.TROUBLESHOOT_GH_PAT }}