Spreadsheet: Background fill color after reaching vertical end

When selecting a cell in the spreadsheet that was added
automatically as per the InfinitelyScrollableTableView
implementation, the background color is now filled correctly.

Previously, when navigating horizontally in a spreadsheet, after
a certain point the cells would not have the same background fill
color as the user would have experienced in the previous column
ranges (A-Z).

Userland/Applications/Spreadsheet/SpreadsheetView.cpp

@@ -173,6 +173,7 @@ SpreadsheetView::SpreadsheetView(Sheet& sheet)
             m_table_view->set_column_width(last_column_index, 50);
             m_table_view->set_default_column_width(last_column_index, 50);
             m_table_view->set_column_header_alignment(last_column_index, Gfx::TextAlignment::Center);
+            m_table_view->set_column_painting_delegate(last_column_index, make<TableCellPainter>(*m_table_view));
         }
         update_with_model();
     };