This reverts commit 59d8d45a.

fix on 20.04:

CMake Error at CMakeLists.txt:103 (add_library):
Target "hpp-centroidal-dynamics" links to target "Boost::Boost" but the
target was not found.  Perhaps a find_package() call is missing for an
IMPORTED target, or an ALIAS target is missing?

run-clang-tidy-6.0.py -header-filter='.*' -checks='llvm-header-guard' -fix