fix doxygen dot graph warning

Author: jef-n

cmake_templates/Doxyfile.in

@@ -1595,7 +1595,7 @@ DOT_GRAPH_MAX_NODES    = 50
 # code bases. Also note that the size of a graph can be further restricted by
 # DOT_GRAPH_MAX_NODES. Using a depth of 0 means no depth restriction.
 
-MAX_DOT_GRAPH_DEPTH    = 0
+MAX_DOT_GRAPH_DEPTH    = 2
 
 # Set the DOT_TRANSPARENT tag to YES to generate images with a transparent
 # background. This is disabled by default, because dot on Windows does not