MPI has passed the tests with cmake 4.0.3, use that as cmake version prefered policy

Author: aminiussi

CMakeLists.txt

@@ -3,7 +3,7 @@
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
-cmake_minimum_required(VERSION 3.5...3.20)
+cmake_minimum_required(VERSION 3.5...4.0)
 
 project(boost_mpi VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES C CXX)