Update archive modals' buttons

This updates the archive/unarchive modals buttons:
* The archive modal's button's label was changed to `Archive project`
  and its variant was set to `warning`.
* The unarchive modal's button's label was changed to `Unarchive project`.

app/views/projects/settings/_archive.html.haml

@@ -10,11 +10,13 @@
     - link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: help_page_path('user/project/settings/index', anchor: 'unarchiving-a-project') }
     %p= _("Unarchiving the project will restore its members' ability to make changes to it. The repository can be committed to, and issues, comments, and other entities can be created. %{strong_start}Once active, this project shows up in the search and on the dashboard.%{strong_end} %{link_start}Learn more.%{link_end}").html_safe % { strong_start: '<strong>'.html_safe, strong_end: '</strong>'.html_safe, link_start: link_start, link_end: '</a>'.html_safe }
     = link_to _('Unarchive project'), unarchive_project_path(@project),
+        aria: { label: _('Unarchive project') },
         data: { confirm: _("Are you sure that you want to unarchive this project?"), qa_selector: 'unarchive_project_link' },
         method: :post, class: "gl-button btn btn-confirm"
   - else
     - link_start = '<a href="%{url}" target="_blank" rel="noopener noreferrer">'.html_safe % { url: help_page_path('user/project/settings/index', anchor: 'archiving-a-project') }
     %p= _("Archiving the project will make it entirely read-only. It is hidden from the dashboard and doesn't show up in searches. %{strong_start}The repository cannot be committed to, and no issues, comments, or other entities can be created.%{strong_end} %{link_start}Learn more.%{link_end}").html_safe % { strong_start: '<strong>'.html_safe, strong_end: '</strong>'.html_safe, link_start: link_start, link_end: '</a>'.html_safe }
     = link_to _('Archive project'), archive_project_path(@project),
-      data: { confirm: _("Are you sure that you want to archive this project?"), qa_selector: 'archive_project_link' },
+      aria: { label: _('Archive project') },
+      data: { confirm: _("Are you sure that you want to archive this project?"), qa_selector: 'archive_project_link', 'confirm-btn-variant': 'warning' },
       method: :post, class: "gl-button btn btn-warning"