Remove regulatory_network.h from biodynamo.h

The header pulls in Boost includes which Cling (ROOT's JIT interpreter)
cannot resolve at runtime on macOS, breaking unrelated tests. As an
optional Boost-based behavior, it should not be auto-included. Users
include core/behavior/regulatory_network.h explicitly in their simulation
code when needed.

Author: sportokalidis

src/biodynamo.h

@@ -31,9 +31,6 @@
 #include "core/behavior/gene_regulation.h"
 #include "core/behavior/growth_division.h"
 #include "core/behavior/secretion.h"
-#ifdef USE_BOOST
-#include "core/behavior/regulatory_network.h"
-#endif
 #include "core/behavior/stateless_behavior.h"
 #include "core/environment/environment.h"
 #include "core/execution_context/copy_execution_context.h"