remove unnecessary method

apps/app/src/server/models/page.ts

@@ -1052,8 +1052,6 @@ schema.methods.calculateAndUpdateLatestRevisionBodyLength = async function(this:
   await this.save();
 };
 
-schema.methods.removeGroupsFromAllPageGrantedGroups = async function(pages: PageDocument[], groupIds: ObjectIdLike[]): Promise<void> {};
-
 /*
  * Merge obsolete page model methods and define new methods which depend on crowi instance
  */