移除已废弃的配置参数login_background_image

config/admin.php

@@ -317,16 +317,6 @@ return [
         'navbar_color' => '',
     ],
 
-    /*
-    |--------------------------------------------------------------------------
-    | Login page background image
-    |--------------------------------------------------------------------------
-    |
-    | This value is used to set the background image of login page.
-    |
-    */
-    'login_background_image' => '',
-
     /*
     |--------------------------------------------------------------------------
     | The exception handler class