Use `$query->{$query->whereInMethod()}()` instead of `$query->whereIn()`

[mpyw]

Laravel has Eager Loading performance tuning strategy against PDO_MYSQL bug, but this library hasn't follow the implementation yet.

• [5.7] Improve eager loading performance by staudenmeir · Pull Request #26453 · laravel/framework
• [5.7] Improve eager loading performance on MySQL by staudenmeir · Pull Request #26434 · laravel/framework

[mpyw]

CC @staudenmeir