posts: fix detection of exif_rotation tag.

`IFD0:Orientation` is the orientation of the main image.
`IFD1:Orientation` is the orientation of the embedded thumbnail, if it
has one. Using `IFD1:Orientation` was incorrect here because some images
have a non-rotated main image but a rotated thumbnail. Post #1023563 is
an example.

app/models/media_asset.rb

@@ -49,8 +49,7 @@ class MediaAsset < ApplicationRecord
 
   # https://exiftool.org/TagNames/EXIF.html
   def is_rotated?
-    metadata["IFD0:Orientation"].in?(["Rotate 90 CW", "Rotate 270 CW", "Rotate 180"]) ||
-    metadata["IFD1:Orientation"].in?(["Rotate 90 CW", "Rotate 270 CW", "Rotate 180"])
+    metadata["IFD0:Orientation"].in?(["Rotate 90 CW", "Rotate 270 CW", "Rotate 180"])
   end
 
   # Some animations technically have a finite loop count, but loop for hundreds