Move the trial onboarding board image to SVG

ee/app/views/registrations/welcome/trial_getting_started.html.haml

@@ -7,5 +7,5 @@
       = image_tag 'learn-gitlab-avatar.jpg', width: '90'
       %h2.gl-text-center.gl-mt-5= _('Get started with GitLab')
       %p.gl-text-center.gl-mb-5= _('We created a sandbox project that will help you learn the basics of GitLab. You’ll be guided by issues in an issue board. You can go through the issues at your own pace.')
-      = image_tag 'trial-learn-gitlab-gold-board.png', class: 'gl-w-full'
+      = image_tag 'board-intro.svg', class: 'gl-w-full'
       = link_to s_("Ok, let's go"), project_boards_path(learn_gitlab_project), class: 'btn btn-success gl-button gl-mt-5'