Configuration GUI: Radio buttons are not supposed to toggle when clic…

…ked, they are supposed to only enter a checked state.

src/libs/gui_tk/gui_tk.h

@@ -2602,7 +2602,7 @@ class Radiobox : public BorderedWindow, public ActionEventSource {
 		(void)y;//UNUSED
 
 		if (button == Left) {
-			checked = !checked;
+			checked = true;
 			execute();
 			return true;
 		}