fix: remove call to non-existent PollService::storyPoll()

The storyPoll() method was never implemented on PollService.
Replace with null to fix phpstan staticMethod.notFound.

Note: Passport::personalAccessClientId() is also flagged but deferred
to a separate PAT refactoring effort.

app/Services/StoryService.php

@@ -61,7 +61,7 @@ class StoryService
                     'media' => url(Storage::url($s->path)),
                     'can_reply' => (bool) $s->can_reply,
                     'can_react' => (bool) $s->can_react,
-                    'poll' => $s->type == 'poll' ? PollService::storyPoll($s->id) : null,
+                    'poll' => null,
                 ];
             })
             ->toArray();