bug#65852: 30.0.50; image-auto-resize :type has choices in wrong order

[Mauro Aranda]

The :type for image-auto-resize looks like this:

:type '(choice (const :tag "No resizing" nil)
               (const :tag "Fit to window" fit-window)
               (other :tag "Scale down to fit window" t)
               (number :tag "Scale factor" 1))

The `other' choice should come last.  Otherwise Custom thinks that
that's the selected option, even when the value of image-auto-resize is
a number.