Revert "feat: Add information on extra attributes on join table in N:M relationships"

This reverts commit 3e52060.

Author: garretaserra

versioned_docs/version-6.x.x/advanced-association-concepts/advanced-many-to-many.md

@@ -368,44 +368,6 @@ Person.belongsToMany(Person, { as: 'Children', through: 'PersonChildren' })
 // This will create the table PersonChildren which stores the ids of the objects.
 ```
 
-## Associations with extra attributes on through table
-
-When creating an N:M association, for example, with User and Project through UserProjects you might want extra attributes in the join table like the "role" attribute . This relationship can be setup like this:
-
-```js
-const User = sequelize.define('User', {
-  username: DataTypes.STRING,
-}, { timestamps: false });
-
-const Project = sequelize.define('Project', {
-  name: DataTypes.STRING
-}, { timestamps: false });
-
-const UserProjects = sequelize.define('UserProjects', {
-  role: DataTypes.STRING
-}, { timestamps: false });
-
-User.belongsToMany(Project, { through: UserProjects})
-Project.belongsToMany(User, { through: UserProjects})
-```
-
-Creating multiple associations with the same extra attributes is possible by passing a single object on the through attribute:
-```js
-user1.setProjects([project1, project2, project3], { through: { role: 'admin' }})
-```
-
-Setting different extra attributes per association can be done by passing an array of objects of the same length as the ammount of associations:
-```js
-user1.setProjects([project1, project2, project3], {
-  through: [
-    { role: 'admin' },
-    { role: 'manager' },
-    { role: 'designer' },
-  ]
-})
-```
-
-
 ## Specifying attributes from the through table
 
 By default, when eager loading a many-to-many relationship, Sequelize will return data in the following structure (based on the first example in this guide):