fix(types): fix `Model.prototype.previous()` (#13042)

types/lib/model.d.ts

@@ -2709,6 +2709,7 @@ export abstract class Model<TModelAttributes extends {} = any, TCreationAttribut
   /**
    * Returns the previous value for key from `_previousDataValues`.
    */
+  public previous(): Partial<TCreationAttributes>;
   public previous<K extends keyof TCreationAttributes>(key: K): TCreationAttributes[K] | undefined;
 
   /**

types/test/model.ts

@@ -184,3 +184,4 @@ expectTypeOf(modelWithAttributes.previous).parameter(0).toEqualTypeOf<keyof Mode
 expectTypeOf(modelWithAttributes.previous).parameter(0).not.toEqualTypeOf<'unreferencedAttribute'>();
 expectTypeOf(modelWithAttributes.previous).returns.toEqualTypeOf<string | number | undefined>();
 expectTypeOf(modelWithAttributes.previous('name')).toEqualTypeOf<string | undefined>();
+expectTypeOf(modelWithAttributes.previous()).toEqualTypeOf<Partial<CreationAttributes>>();