Fix YouTube embed link
Why is this change being made?
On the current version of https://about.gitlab.com/releases/gitlab-com/#importing-from-github-defaults-to-the-current-group-path on Firefox, the following is shown:
Looking at some recent release posts that use YT embeds, the https://www.youtube.com/embed/<videoId>
format is used: https://gitlab.com/gitlab-com/www-gitlab-com/-/blob/1db594f9ebd57d7a4bc138b90d51d86db69059fb/data/release_posts/14_8/verify_cicd_home_mvc__static_validation.yml#L7
/cc @ngaskill