erp5_project: fix column name

task_line_quantity_unit_title somehow doesn't work for all

bt5/erp5_project/SkinTemplateItem/portal_skins/erp5_project/Project_viewTaskList/listbox.xml

@@ -164,11 +164,11 @@
                           <string>End Date</string>
                         </tuple>
                         <tuple>
-                          <string>quantity</string>
+                          <string>task_line_quantity</string>
                           <string>Estimated Time</string>
                         </tuple>
                         <tuple>
-                          <string>quantity_unit_title</string>
+                          <string>task_line_quantity_unit</string>
                           <string>Unit</string>
                         </tuple>
                         <tuple>