Remove wxTreeListCtrl special first column resizing logic

Trying to give all the remaining space after allocating enough to the
other columns to the first one doesn't work well with wxDataViewCtrl,
which tries to do the same thing, but with the last column, so we
actually get some strange mix of behaviours, with both the first and
last columns changing size after the control itself is resized.

Stop fighting with wxDataViewCtrl and just let it to its own thing.

Closes #17476.

src/generic/treelist.cpp

@@ -1455,28 +1455,6 @@ void wxTreeListCtrl::OnSize(wxSizeEvent& event)
         view->Refresh();
         view->Update();
 #endif // wxHAS_GENERIC_DATAVIEWCTRL
-
-        // Resize the first column to take the remaining available space.
-        const unsigned numColumns = GetColumnCount();
-        if ( !numColumns )
-            return;
-
-        // There is a bug in generic wxDataViewCtrl: if the column width sums
-        // up to the total size, horizontal scrollbar (unnecessarily) appears,
-        // so subtract a bit to ensure this doesn't happen.
-        int remainingWidth = rect.width - 5;
-        for ( unsigned n = 1; n < GetColumnCount(); n++ )
-        {
-            remainingWidth -= GetColumnWidth(n);
-            if ( remainingWidth <= 0 )
-            {
-                // There is not enough space, as we're not going to give the
-                // first column negative width anyhow, just don't do anything.
-                return;
-            }
-        }
-
-        SetColumnWidth(0, remainingWidth);
     }
 }