Fix wrong type definition on lean function parameter (#35916)

* Fix wrong type definition on lean function parameter

* Update the parameter type in lean function

types/mongoose/index.d.ts

@@ -24,6 +24,7 @@
 //                 Erik Lopez <https://github.com/niuware>
 //                 Vlad Melnik <https://github.com/vladmel1234>
 //                 Jarom Loveridge <https://github.com/jloveridge>
+//                 Grimmer Kang <https://github.com/grimmer0125>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
@@ -1935,9 +1936,9 @@ declare module "mongoose" {
      * Documents returned from queries with the lean option enabled are plain
      * javascript objects, not MongooseDocuments. They have no save method,
      * getters/setters or other Mongoose magic applied.
-     * @param bool defaults to true
+     * @param {Boolean|Object} bool defaults to true
      */
-    lean(bool?: boolean): Query<any> & QueryHelpers;
+    lean(bool?: boolean | object): Query<any> & QueryHelpers;
 
     /** Specifies the maximum number of documents the query will return. Cannot be used with distinct() */
     limit(val: number): this;

types/mongoose/mongoose-tests.ts

@@ -1199,6 +1199,12 @@ query.
   sort('-occupation').
   select('name occupation').
   exec(cb).then(cb).catch(cb);
+/**
+ * https://mongoosejs.com/docs/api.html#query_Query-lean
+ */
+query.lean() // true
+query.lean(false)
+query.lean({})
 
 /*
  * section schema/array.js