Revert "Add GitHub Actions workflow for syncing upstream"

This reverts commit 5ffd84b57d.

sync-upstream.yml

@@ -1,34 +0,0 @@
-name: 同步冰朔上游仓库
-
-on:
-  schedule:
-    - cron: '0 2 * * *'
-  workflow_dispatch:
-
-jobs:
-  sync:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-          token: $ secrets.GITHUB_TOKEN 
-
-      - name: 配置 Git
-        run: |
-          git config user.name "github-actions[bot]"
-          git config user.email "github-actions[bot]@users.noreply.github.com"
-
-      - name: 添加上游仓库
-        run: |
-          git remote add upstream https://github.com/qinfendebingshuo/guanghulab.git || true
-          git fetch upstream
-
-      - name: 合并上游更新
-        run: |
-          git checkout main
-          git merge upstream/main --no-edit --allow-unrelated-histories
-
-      - name: 推送
-        run: git push origin main