Do extra docs validation; explicitly disallow semantic markup in docs (#6345)
* Do extra docs validation. Explicitly disallow semantic markup in docs.
* Forgot to add new requirement.
* Fix prefixes.
* Remove superfluous condition.
* TEMP - make CI fail.
* Revert "TEMP - make CI fail."
This reverts commit 14f4d6b503.
* Remove unnecessary import.
* Make sure ANSIBLE_COLLECTIONS_PATH is set.
* Make sure sanity tests from older Ansible versions don't complain.
(cherry picked from commit ee11847c7e)
Co-authored-by: Felix Fontein <felix@fontein.de>