* docs: remove obsolete reference to `gen_tags.sh`
`scripts/gen_tags.sh` was removed in 373b952a0c
* docs: fix 404 links
Merge the `Requirements` section with the `Usage` section and just
reference the inventory documentation, which then points to all further
information related to group vars etc.
* Remove checks for docs using exact tags
Instead use a more generic documentation for installing kubespray as a
collection from git.
* Check that we upgraded galaxy.yml to next version
This is only intented to check for human error. The version in galaxy
should be the next (which does not mean the same if we're on master or a
release branch).
* Set collection version to KUBESPRAY_NEXT_VERSION