fix: use stdlib free instead of malloc

malloc.h isn't portable to MacOS
https://stackoverflow.com/questions/12973311/difference-between-stdlib-h-and-malloc-h

compiler/lib/ClientLib/Serializers.cpp

@@ -3,8 +3,6 @@
 // https://github.com/zama-ai/concrete-compiler-internal/blob/master/LICENSE.txt
 // for license information.
 
-#include <malloc.h>
-
 #include <iosfwd>
 #include <iostream>
 #include <stdlib.h>