Remove system from the list of boost lib to be found

[sloriot]

Remove it from here:

libpointmatcher/libpointmatcherConfig.cmake.in

Line 12 in c44ce31

find_package(Boost COMPONENTS thread system program_options date_time chrono REQUIRED)

I think it's a leftover from the boost filesystem removal (after checking boost headers included).

It is an issue because in boost master, system is no longer a library and this causes issues
when multiple versions of boost are installed on the system