Modified misleading text about CKFinder maximum image size setting

I did not know that CKfinder had an option to configure the maximum width and height of uploaded images.

This was because the help tekst in Settings > General > CKFinder: Maximum width/height was misleading.
The text told us that you could configure the maximum width and height for the editor itself.
This text is wrong, so I updated the text.

I have checked the english and dutch translation. Other languages are translated using google translate. Can someone please check the languages: russian, german, spanish, hungary, greek, chinese?