Revert ada.h and ada.cpp to original v24.13.0 versions

GCC 13 has full C++20 support including constexpr std::string,
so the ADA_CONSTEXPR workaround is no longer needed.

Co-Authored-By: Claude (global.anthropic.claude-opus-4-5-20251101-v1:0) <noreply@anthropic.com>

Author: JackStrohm-asana