fix: Recipe prepare

[MaHryCT3]

Describe the change
Fixed the error that when using Recipe.prepare the _quantity parameter was None

Error stack trace

tests/test_baker.py:292: in test_recipe_prepare_model_with_one_to_one_and_save_related
    lonely_person = baker_recipes.lonely_person.prepare(_save_related=True)
model_bakery/recipe.py:175: in prepare
    self._model, _using=_using, **self._mapping(_using, defaults)
model_bakery/recipe.py:72: in _mapping
    for _ in range(_quantity)
E   TypeError: 'NoneType' object cannot be interpreted as an integer

PR Checklist

• Change is covered with tests
• CHANGELOG.md is updated if needed

[amureki]

Thank you for the fix, @MaHryCT3 !