fix: rename id to stratigraphy for model block

Author: lachlangrose

LoopStructural/modelling/core/geological_model.py

@@ -1807,5 +1807,7 @@ def get_stratigraphic_surfaces(self, units: List[str] = [], bottoms: bool = True
     def get_block_model(self):
         grid = self.bounding_box.vtk
 
-        grid.cell_data['id'] = self.evaluate_model(self.bounding_box.cell_centers(), scale=False)
+        grid.cell_data['stratigraphy'] = self.evaluate_model(
+            self.bounding_box.cell_centers(), scale=False
+        )
         return grid, self.stratigraphic_ids()