Fix link to upgrade assistant

This broke when stack management changed their URLs.

Author: smith

x-pack/plugins/apm/public/setHelpExtension.ts

@@ -20,10 +20,7 @@ export function setHelpExtension({ chrome, http }: CoreStart) {
       },
       {
         linkType: 'custom',
-        href: url.format({
-          pathname: http.basePath.prepend('/app/kibana'),
-          hash: '/management/stack/upgrade_assistant',
-        }),
+        href: http.basePath.prepend('/app/management/stack/upgrade_assistant'),
         content: i18n.translate('xpack.apm.helpMenu.upgradeAssistantLink', {
           defaultMessage: 'Upgrade assistant',
         }),