SOCI's vendored conanfile was using boost::boost which links against
every single Boost library (40+ libraries) when only boost::headers
is needed for SOCI's template specializations (boost::optional and
boost::gregorian::date support).
This was causing excessive linking and potential symbol conflicts,
particularly on Linux CI where boost_stacktrace_from_exception was
causing multiple definition errors with libstdc++.
Changed SOCI's boost dependency from boost::boost to boost::headers
since SOCI only needs Boost headers for its template specializations,
not the compiled libraries. The project already provides all necessary
Boost libraries through the ripple_boost target.
This reduces the linked libraries from 40+ down to just the ~14 that
the project actually uses, fixing the Linux CI build failures and
reducing binary size.
Note: The SOCI Conan recipe for Conan 2.0 already implements this
fix correctly.
