tests: Remove Windows/Linux hostname manipulation

It is unclear in what circumstances this manipulation is required and we do not test it in our CI. As the comment suggests that this is to do with compatibility between Windows and Linux and the hostnames come from cmake_host_system_information it seems more appropriate that this should be done in CMake if it is actually required.

Also, this manipulation assumes that here is a '.' in the hostname and will crash if this is not the case.

For now, we remove this from the C++ tests with a plan to add something to the CMakeLists.txt file if, in the future, it turns out that the hostnames are actually not compatible between operating systems.