Update pull request template to match latest prow capabilities
Update pull request template to match latest prow capabilities

Prow is now able to strip HTML comments for `kind/*` labels,
which means that we can sync-up with the official k/k pull request
template.

Signed-off-by: Sascha Grunert <70ab469ddb2ac3e35f32ed7c2fd1cca514b2e879@suse.com>

kubernetes/release,kubernetes/release