Update alert to use alert-specific classes

- gl-alert-body and gl-alert-actions
- remove unnecessary html-safe

app/views/shared/_auto_devops_implicitly_enabled_banner.html.haml

 - if show_auto_devops_implicitly_enabled_banner?(project, current_user)
   .qa-auto-devops-banner.auto-devops-implicitly-enabled-banner.gl-alert.gl-alert-info
-    = sprite_icon('information-o', size: 16, css_class: 'gl-icon gl-alert-icon gl-alert-icon-no-title')
-    - auto_devops_message = s_("AutoDevOps|The Auto DevOps pipeline has been enabled and will be used if no alternative CI configuration file is found.")
-    = auto_devops_message.html_safe
+    = sprite_icon('information-o', css_class: 'gl-icon gl-alert-icon gl-alert-icon-no-title')
     %button.js-close.gl-alert-dismiss{ type: 'button', 'aria-label' => _('Dismiss'), class: 'hide-auto-devops-implicitly-enabled-banner alert-link', data: { project_id: project.id } }
       = sprite_icon('close', css_class: 'gl-icon')
+    .gl-alert-body
+      = s_("AutoDevOps|The Auto DevOps pipeline has been enabled and will be used if no alternative CI configuration file is found.")
     - unless Gitlab.config.registry.enabled
       %div
         = _('Container registry is not enabled on this GitLab instance. Ask an administrator to enable it in order for Auto DevOps to work.')
-    .gl-mt-3
+    .gl-alert-actions.gl-mt-3
       = link_to _('Settings'), project_settings_ci_cd_path(project), class: 'alert-link btn gl-button btn-info'
       = link_to _('More information'), help_page_path('topics/autodevops/index.md'), target: '_blank', class: 'alert-link btn gl-button btn-default gl-ml-2'