Remove main-to-master-sync workflow (upstream cruft; fork uses main)

.github/workflows/main-to-master-sync.yml

@@ -1,22 +0,0 @@
-name: Sync Main to Master
-
-on:
-  push:
-    branches:
-      - main
-
-jobs:
-  sync:
-    runs-on: ubuntu-latest
-
-    steps:
-    - name: Checkout repository
-      uses: actions/checkout@v6
-      with:
-        ref: main
-        fetch-depth: 0
-
-    - name: Push changes to master
-      run: |
-        git checkout -b master
-        git push origin +master