Update system_theme.png

[alain01]

Resized in 60x60 like other icons
If no resize, there is a BIIIG icon on the display, when we choose transition or dark theme (other than cpadmin)

[mambax7]

Don't forget to always create equivalent icons for the Default theme, otherwise, when I choose the default icons, I get this:

[alain01]

Ok, I added the icon. Thank you
But it's strange, before that, I chose default admin theme and I was able to see the icon.
The link was '/modules/system/images/icons/transition/xoops/system_theme.png'.
I deleted cache and images on my browser and same.
Need an explanation if it's possible ! ;-)