plasma: rename Auros wallpaper image to match its size

incorrect since before the fork

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>

diff --git a/plasma/wallpapers/data/Auros/contents/images/1024x748.png b/plasma/wallpapers/data/Auros/contents/images/1024x768.png
similarity index 100%
rename from plasma/wallpapers/data/Auros/contents/images/1024x748.png
rename to plasma/wallpapers/data/Auros/contents/images/1024x768.png