pixiv: avoid unnecessary API call when uploading Pixiv posts.

Do one less API call when fetching the image URLs for a Pixiv post. The
`is_ugoira?` check in `image_urls` caused us to do an extra API call
when fetching the image URLs for a non-ugoira post.

API calls to Pixiv take around ~800ms, so this reduces minimum upload
time for Pixiv posts from ~1.6 seconds (two calls) to ~0.8 seconds.

app/logical/sources/strategies/pixiv.rb

@@ -223,7 +223,7 @@ module Sources
 
       def is_ugoira?
         # https://i.pximg.net/img-original/img/2019/05/27/17/59/33/74932152_ugoira0.jpg
-        url.match?(UGOIRA) || api_illust.dig(:urls, :original)&.match?(/ugoira/)
+        url.match?(UGOIRA) || original_urls&.any?(/ugoira/)
       end
 
       def illust_id