gtk: Strip newlines from g_warning and g_error

g_logv adds one for us already.

gtk/gtkmountoperation-x11.c

@@ -160,7 +160,7 @@ get_utf8_property (Display *xdisplay,
 
   if (!g_utf8_validate (val, nitems, NULL))
     {
-      g_warning ("Property %s contained invalid UTF-8\n",
+      g_warning ("Property %s contained invalid UTF-8",
                  gdk_x11_get_xatom_name (atom));
       XFree (val);
       return NULL;