Document that wxTreeCtrl::ScrollTo() doesn't work when frozen

Also mention that EnsureVisible() does work in this case.

See #18435.

interface/wx/treectrl.h

@@ -371,6 +371,9 @@ public:
 
     /**
         Scrolls and/or expands items to ensure that the given item is visible.
+
+        This method can be used, and will work, even while the window is frozen
+        (see wxWindow::Freeze()).
     */
     virtual void EnsureVisible(const wxTreeItemId& item);
 
@@ -797,6 +800,11 @@ public:
 
     /**
         Scrolls the specified item into view.
+
+        Note that this method doesn't work while the window is frozen (See
+        wxWindow::Freeze()), at least under MSW.
+
+        @see EnsureVisible()
     */
     virtual void ScrollTo(const wxTreeItemId& item);