refactor(national-motion-system-biz): 移除 AppCourses 类中的库存字段

移除了 AppCourses 类中的 inventory 字段，该字段不再需要。

national-motion-module-system/national-motion-system-biz/src/main/java/org/jeecg/modules/system/app/entity/AppCourses.java

@@ -112,9 +112,6 @@ public class AppCourses implements Serializable {
     @Excel(name = "上架状态;0上架 1下架", width = 15)
     @Schema(description = "上架状态;0上架 1下架")
     private java.lang.Integer rackingStatus;
-    @Excel(name = "库存", width = 15)
-    @Schema(description = "库存")
-    private java.lang.Integer inventory;
     /**视频*/
     @Excel(name = "视频", width = 15)
     @Schema(description = "视频")