Remove obsolete note about limited wxFileDataObject support

This class seems to be implemented in all the major ports, so remove
note saying that it supports dragging files from the applications only
under MSW.

Closes #18437.

interface/wx/dataobj.h

@@ -753,15 +753,9 @@ public:
     wxFileDataObject is a specialization of wxDataObject for file names. The
     program works with it just as if it were a list of absolute file names, but
     internally it uses the same format as Explorer and other compatible
-    programs under Windows or GNOME/KDE filemanager under Unix which makes it
+    programs under Windows or GNOME/KDE file manager under Unix which makes it
     possible to receive files from them using this class.
 
-    @warning Under all non-Windows platforms this class is currently
-             "input-only", i.e. you can receive the files from another
-             application, but copying (or dragging) file(s) from a wxWidgets
-             application is not currently supported. PS: GTK2 should work as
-             well.
-
     @library{wxcore}
     @category{dnd}