Fix build with boost 1.84

Index: OrthancFramework/Sources/Toolbox.h
--- OrthancFramework/Sources/Toolbox.h.orig
+++ OrthancFramework/Sources/Toolbox.h
@@ -27,6 +27,7 @@
 #include "Enumerations.h"
 #include "OrthancFramework.h"
 
+#include <cassert>
 #include <stdint.h>
 #include <vector>
 #include <string>
