Fix object hierarchy graph

Matlab/Matlab.md

@@ -474,10 +474,10 @@ fig = gcf;    % get handle to current figure
 ### Typical object hierarchy
 
 ```mermaid
-graph Structure;
-  Figure-->Legend;
-  Figure-->Axes;
-  Axes-->Lines;
+graph TD
+  Figure --> Legend
+  Figure --> Axes
+  Axes --> Lines
 ```
 
 ### Set color