Thumbnailer frequently rejecting portrait mode images

[kulmann]

Describe the bug

With #9069 scan limitations for image width and height were introduced to the thumbnail service. However, the width to height aspect ratio is favouring landscape mode images over portrait mode images. ;-)

Steps to reproduce

1. Upload a portrait mode image from a low price segment DSLR
2. Try to see a thumbnail or open the image in the preview app

Expected behavior

Our defaults work for thumbnail generation for images from for this kind of camera

Actual behavior

Our defaults are too restrictive for portrait mode images
Image width and height should be the same value, so that thumbnail generation works for both landscape and portrait mode images.

[jnweiger]

See also: https://central.owncloud.org/t/cannot-view-vertical-photos-on-the-web-side/47758/2