Fix video attachment window size

We need it to be as wide as the other attachments
in order for the file info text disaply to work.

Signed-off-by: Thomas von Deyen <vondeyen@blish.cloud>

Author: tvdeyen

app/helpers/alchemy/admin/attachments_helper.rb

@@ -15,7 +15,7 @@ def attachment_preview_size(attachment)
         when "application/pdf" then "850x600"
         when *IMAGE_FILE_TYPES then "850x280"
         when *AUDIO_FILE_TYPES then "850x190"
-        when *VIDEO_FILE_TYPES then "900x280"
+        when *VIDEO_FILE_TYPES then "850x240"
         else
           "500x165"
         end