[QA] Fix resource API fabrication documentation
[QA] Fix resource API fabrication documentation

The precedence of methods to fetch a product's attribute value was changed recently:

1. API response
2. Web UI block
3. Inheritance from the factory
4. Raise a `QA::Factory::Product::NoValueError` error otherwise
mmkassem/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,iiet/iiet-git,stoplightio/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,dreampet/gitlab,iiet/iiet-git,dreampet/gitlab,mmkassem/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git