Fix MYSQL Many To Many relation when try to detach

[nouraraar91]

right now when implementing the relationship Many-to-Many with MySql, all is working but when trying to detach from the MySQL model an error BadMethodCallException with message 'Call to undefined method App\Models\User::pull()' is showing because that MySQL model is not a collection and can't use pull on it

so I added a check to see if the model is a mongo collection or not and then will call the pull method similar issues: #2002

I am not sure how I should create a Pull request here, I couldn't push my branch to create the PR

[Smolevich]

after pushing your branch in your fork, github automatically suggests create PR to this repo