fix: pr update must edit assignee login

app/controllers/pull_requests_controller.rb

@@ -274,10 +274,11 @@ class PullRequestsController < ApplicationController
       base: params[:base],  #目标分支
       milestone: 0,  #里程碑,未与本地的里程碑关联
     }
+    assignee_login = User.find_by_id(params[:assigned_to_id])&.login
     @requests_params = @local_params.merge({
-      assignee: current_user.try(:login),
+      assignee: assignee_login,
       # assignees: ["#{params[:assigned_login].to_s}"],
-      assignees: ["#{current_user.try(:login).to_s}"],
+      assignees: ["#{assignee_login.to_s}"],
       labels: params[:issue_tag_ids],
       due_date: Time.now
     })