ci: remove a Git repository mirroring GitHub action

.github/workflows/main.yml

@@ -1,19 +0,0 @@
-# Sync repo to the Codeberg mirror
-name: Repo sync GitHub -> SVR.JS Git server
-on:
-  push:
-    branches:
-    - '**'
-
-jobs:
-  svrjsgit:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          fetch-depth: 0
-      - uses: spyoungtech/mirror-action@v0.5.1
-        with:
-          REMOTE: "https://git.svrjs.org/svrjs/svrjs-mod-starter.git"
-          GIT_USERNAME: github-mirror
-          GIT_PASSWORD: ${{ secrets.GIT_PASSWORD }}