fix: silence clang deprecation warnings in json.hpp

[vmobilis]

Summary

Clang complains that spaces in declarations of literal operators are deprecated:

json.hpp:24314:35: warning: identifier '_json' preceded by whitespace in a literal operator declaration is deprecated [-Wdeprecated-literal-operator]
 24314 | inline nlohmann::json operator "" _json(const char* s, std::size_t n)
       |                       ~~~~~~~~~~~~^~~~~
       |                       operator""_json

Additional Information

It's not a complete update of a third party dependency, so I hope it doesn't need to open a discussion first.
And thank you.

Checklist

• I have read and confirmed this PR follows the contribution guidelines.