Fixed Analytics > Newsletters chart loading (#24566)

ref https://linear.app/ghost/issue/ENG-2493/
ref
31932c5
- formatDisplayDate was being called with a Date object instead of date
string

We updated date formatting to ingest localized dates as localized dates
and UTC dates as UTC dates, however we introduced a string function that
broke the call when used with a Date object instead of date string. The
previous implementation did not have this trouble. I would've expected
the Typescript build to fail here - I will have to look in to that.

Author: 9larsons

apps/stats/src/views/Stats/Newsletters/Newsletters.tsx

@@ -85,7 +85,7 @@ const NewsletterTableRows: React.FC<{
                                 </div>
                             </TableCell>
                             <TableCell className="whitespace-nowrap text-sm">
-                                {formatDisplayDate(new Date(post.send_date))}
+                                {formatDisplayDate(post.send_date)}
                             </TableCell>
                             <TableCell className='text-right font-mono text-sm'>
                                 {formatNumber(post.sent_to)}