Resolve spec failure in spec/helpers/issuables_helper_spec.rb

Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/helpers/issuables_helper_spec.rb

@@ -212,6 +212,7 @@ describe IssuablesHelper do
         issuableRef: "&#{epic.iid}",
         markdownPreviewPath: "/groups/#{@group.full_path}/preview_markdown",
         markdownDocsPath: '/help/user/markdown',
+        markdownVersion: 11,
         issuableTemplates: nil,
         groupPath: @group.path,
         initialTitleHtml: epic.title,