Fix TileMap::set_pattern offsets

Currently it is trying to use the target coordinates (i.e., in the destination TileMap) to pull from the pattern, rather than the pattern-local coordinates.

scene/2d/tile_map.cpp

@@ -2143,7 +2143,7 @@ void TileMap::set_pattern(int p_layer, Vector2i p_position, const Ref<TileMapPat
 	TypedArray<Vector2i> used_cells = p_pattern->get_used_cells();
 	for (int i = 0; i < used_cells.size(); i++) {
 		Vector2i coords = map_pattern(p_position, used_cells[i], p_pattern);
-		set_cell(p_layer, coords, p_pattern->get_cell_source_id(coords), p_pattern->get_cell_atlas_coords(coords), p_pattern->get_cell_alternative_tile(coords));
+		set_cell(p_layer, coords, p_pattern->get_cell_source_id(used_cells[i]), p_pattern->get_cell_atlas_coords(used_cells[i]), p_pattern->get_cell_alternative_tile(used_cells[i]));
 	}
 }