cmake policy with required cmake version

[thomas-lemaire]

In geometry-central/deps/CMakeLists.txt the required minimal cmake version is 3.8 whereas line 3 the CMP0169 policy is used. This policy is only part of newer cmake from version 3.30 (cf https://cmake.org/cmake/help/latest/policy/CMP0169.html)

By the way depending on such a new cmake version make a decent Ubuntu 24.04 system not compatible, it ships cmake 3.28