Final call: make visible text content definition objective #1419

Hey folks,
This PR fixes an issue, where we used a subjective definition in the
applicability. Please have a look. This final call ends on August 31st. If
you have any feedback, please leave a review before that date:

https://github.com/act-rules/act-rules.github.io/pull/1419

-- 
*Wilco Fiers*
Axe for Web product owner - Co-facilitator WCAG-ACT - Chair ACT-R