5.0.5 release forgot to bump CMake version variables

https://gitlab.com/ubports/development/core/lib-cpp/dbus-cpp/-/blob/5.0.5/CMakeLists.txt?ref_type=tags#L21-23

set(DBUS_CPP_VERSION_MAJOR 5)
set(DBUS_CPP_VERSION_MINOR 0)
set(DBUS_CPP_VERSION_PATCH 4)

This previously was the same as the release version, now it isn't anymore. Affects the version displayed in the documentation, the full solib version, and the version returned via pkg-config queries.