Update nlohman/json library from 3.10.2 (released 2021-08-26) to 3.11.2
(released 2022-08-12). No specific reason for an update, just to keep
libraries up-to-date.
Release logs: https://github.com/nlohmann/json/releases
Note: The library may use `std::filesystem` now, which was an issue on
macOS for Blender before. Availability is checked first though, so this
should be fine.