[markdown] Use older version of mdl (0.9)
[markdown] Use older version of mdl (0.9)

https://github.com/markdownlint/markdownlint/issues/344

Signed-off-by: Martin Bašti <388356a3851efe39ff0604de6d8fb2e16e10a0b7@redhat.com>

release-engineering/koji-containerbuild,release-engineering/koji-containerbuild