Update appdata screenshot
https://gitlab.gnome.org/GNOME/eog/raw/master/data/screenshot.png is the screenshot listed in Eog's appdata file, which is quite outdated (theme changes, zoom controls missing in the top right...)
This is a good opportunity for newcomers to learn how to make their first contribution to a GNOME application.
For the screenshot, please read the specs at https://www.freedesktop.org/software/appstream/docs/chap-Quickstart.html#qsr-app-screenshots-info and make sure to use the upstream theme, the default close button arrangement, besides aspect-ratio, file format, resolution, etc...