Remove unnecessary methods of wxCocoaOutlineDataSource.

{append,remove}Child() were never used, remove them to make it easier to
remove the use of "children" array itself later (see #16740).

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78294 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/cocoa/dataview.h

@@ -314,11 +314,9 @@ private:
     -(void)             removeFromBuffer:(wxPointerObject*)item;
 
     // buffered children handling
-    -(void)             appendChild:(wxPointerObject*)item;
     -(void)             clearChildren;
     -(wxPointerObject*) getChild:(NSUInteger)index;
     -(NSUInteger)       getChildCount;
-    -(void)             removeChild:(NSUInteger)index;
 
     // buffer handling
     -(void) clearBuffers;

src/osx/cocoa/dataview.mm

@@ -1039,11 +1039,6 @@ outlineView:(NSOutlineView*)outlineView
 //
 // children handling
 //
--(void) appendChild:(wxPointerObject*)item
-{
-    [children addObject:item];
-}
-
 -(void) clearChildren
 {
     [children removeAllObjects];
@@ -1059,11 +1054,6 @@ outlineView:(NSOutlineView*)outlineView
     return [children count];
 }
 
--(void) removeChild:(NSUInteger)index
-{
-    [children removeObjectAtIndex:index];
-}
-
 //
 // buffer handling
 //