fix：😀修复InvalidOperationException异常

Admin.NET/Plugins/Admin.NET.Plugin.ApprovalFlow/Middleware/ApprovalFlowMiddleware.cs

@@ -34,16 +34,17 @@ public class ApprovalFlowMiddleware
     private readonly RequestDelegate _next;
     private readonly SysApprovalService _sysApprovalService;
 
-    public ApprovalFlowMiddleware(RequestDelegate next, SysApprovalService sysApprovalService)
+    public ApprovalFlowMiddleware(RequestDelegate next)
     {
         _next = next;
-        _sysApprovalService = sysApprovalService;
+        _sysApprovalService = App.GetRequiredService<SysApprovalService>();
     }
 
-    public async Task Invoke(HttpContext context)
+    public async Task InvokeAsync(HttpContext context)
     {
         await _sysApprovalService.MatchApproval(context);
 
-        await _next.Invoke(context);
+        // 调用下一个中间件
+        await _next(context);
     }
 }