ci(workflow): 移除重复的Flutter设置步骤并修复格式

.gitea/workflows/docker.yml

@@ -158,13 +158,7 @@ jobs:
         Write-Host "📄 验证文件："
         if (Test-Path libcore/bin) {
           Get-ChildItem libcore/bin -ErrorAction SilentlyContinue | Format-Table Name, Length
-        }
+        }\n\n    - name: Setup Flutter\n      uses: subosito/flutter-action@v2\n      with:\n        flutter-version: '3.24.5'\n        channel: 'stable'
-
-        - name: Setup Flutter
-          uses: subosito/flutter-action@v2
-          with:
-            flutter-version: '3.24.5'
-            channel: 'stable'
         
         - name: Enable Windows desktop
           run: flutter config --enable-windows-desktop