Fix Google Translate breaking web interface (#15610)

- marks the page as a whole as untranslatable
- still marks user text as translatable

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/mastodon/features/getting_started/components/announcements.js

@@ -145,7 +145,7 @@ class Content extends ImmutablePureComponent {
 
     return (
       <div
-        className='announcements__item__content'
+        className='announcements__item__content translate'
         ref={this.setRef}
         dangerouslySetInnerHTML={{ __html: announcement.get('contentHtml') }}
       />