In the previous version, 1.18.0, the "megacheck" linter paid attention
to the '//lint:ignore' comment, but that is no longer there.
Newer version pay attention to '//nolint:<linter>,<linter>,...'
comments, optionally followed by a "second" comment introduced by '//'.
Update the directives to use this style.
This is related to prometheus/blackbox_exporter#738 and
prometheus/blackbox_exporter#745.
Signed-off-by: Marcelo E. Magallon <marcelo.magallon@grafana.com>