Group `validates_associated` documentation with `validates_*` [ci-skip]
Group `validates_associated` documentation with `validates_*` [ci-skip]

`validates_associated` makes sure that passed associations are validated
everytime the record is saved. This is unlike other validations that
validate an attribute/association has a certain value.
Typically you won't call:

    validates :books, associated: true

By grouping `validates_associated` with `validates_with` and
`validates_each` it's made clearer `validates_associated` is a bit
different.

With this change the validations are sorted alphabetically.

georgeclaghorn/rails,Erol/rails,rails/rails,Edouard-chin/rails,BlakeWilliams/rails,georgeclaghorn/rails,Edouard-chin/rails,kmcphillips/rails,Erol/rails,esparta/rails,yawboakye/rails,rails/rails,yawboakye/rails,MSP-Greg/rails,Edouard-chin/rails,kmcphillips/rails,Erol/rails,georgeclaghorn/rails,kmcphillips/rails,yahonda/rails,BlakeWilliams/rails,georgeclaghorn/rails,Edouard-chin/rails,yahonda/rails,yawboakye/rails,esparta/rails,MSP-Greg/rails,rails/rails,BlakeWilliams/rails,kmcphillips/rails,yawboakye/rails,esparta/rails,BlakeWilliams/rails,esparta/rails,yahonda/rails,yahonda/rails,MSP-Greg/rails,rails/rails,Erol/rails,MSP-Greg/rails