Fix min boost version

CMakeLists.txt

@@ -71,7 +71,7 @@ set( Boost_USE_STATIC_LIBS OFF )
 set( Boost_USE_MULTITHREADED ON )
 set( Boost_USE_STATIC_RUNTIME OFF )
 
-find_package( Boost 1.72.0 COMPONENTS mpi timer serialization system )
+find_package( Boost 1.71 COMPONENTS mpi timer serialization system )
 
 #
  # Generate the config.h