Remove syncing master from main

.github/workflows/update-master-after-main.yml

@@ -1,17 +0,0 @@
-name: Updates the master branch after changes in the main branch
-on:
-  push:
-    branches:
-      - main
-
-jobs:
-  mirror:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-        with:
-          fetch-depth: 0
-      - name: Push
-        run: |
-          git push origin HEAD:master