* update dockerfiles to use latest stable syntax
Some Dockerfiles were pinned to a minor release, which meant they
wouldn't be updated to get the latest stable syntax (and fixes),
and one Dockerfile used the "labs" variant to use the HEREDOC syntax,
which has now been promoted to the stable syntax.
* docs: rename Dockerfile
There's no other Dockerfiles in the same path, so the "docs"
prefix was redundant.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Sebastiaan van Stijn