Update YCMBootstrapFetch.cmake to avoid CMP0169 related warnings and update YCM to 0.17.1

[traversaro]

This will remove all the noisy warnings:

CMake Warning (dev) at D:/miniforge3/envs/robsub/Library/share/[cmake-3](https://gitlab.kitware.com/cmake/cmake/-/issues/3).30/Modules/FetchContent.cmake:1953 (message):
Calling FetchContent_Populate(YCM) is deprecated, call
FetchContent_MakeAvailable(YCM) instead. Policy CMP0169 can be set to OLD
to allow FetchContent_Populate(YCM) to be called directly for now, but the
ability to call it with declared details will be removed completely in a
future version.
Call Stack (most recent call first):
cmake/YCMBootstrapFetch.cmake:103 (FetchContent_Populate)
CMakeLists.txt:60 (include)

in recent CMake releases.

[traversaro]

This highlighted a bug that was fixed in robotology/ycm-cmake-modules#464 .