docs(model): findOne return value for empty result (#11762)

lib/model.js

@@ -1893,9 +1893,7 @@ class Model {
   }
 
   /**
-   * Search for a single instance. This applies LIMIT 1, so the listener will always be called with a single instance.
-   *
-   * __Alias__: _find_
+   * Search for a single instance. Returns the first instance found, or null if none can be found.
    *
    * @param  {object}       [options] A hash of options to describe the scope of the search
    * @param  {Transaction}  [options.transaction] Transaction to run query under
@@ -1904,7 +1902,7 @@ class Model {
    * @see
    * {@link Model.findAll} for an explanation of options
    *
-   * @returns {Promise<Model>}
+   * @returns {Promise<Model|null>}
    */
   static findOne(options) {
     if (options !== undefined && !_.isPlainObject(options)) {

types/lib/model.d.ts

@@ -1789,8 +1789,7 @@ export abstract class Model<T = any, T2 = any> extends Hooks {
   ): Promise<M | null>;
 
   /**
-   * Search for a single instance. This applies LIMIT 1, so the listener will always be called with a single
-   * instance.
+   * Search for a single instance. Returns the first instance found, or null if none can be found.
    */
   public static findOne<M extends Model>(this: { new (): M } & typeof Model, options: NonNullFindOptions): Promise<M>;
   public static findOne<M extends Model>(