A .jedi/project.json can be part of a checked out repository, so honouring its environment_path let an untrusted file point Jedi at a binary to execute. Rather than trying to gate that binary (the ownership heuristic in _is_unix_safe_simple is meaningless on Windows, where st_uid is always 0), drop environment_path from loaded project files entirely, the same way load_unsafe_extensions is already ignored. It stays available when a Project is constructed directly by the user.
get_default_project() loads the first .jedi/project.json above the analysed file, which can be part of a checked out repository. Its environment_path was executed with safe=False and its load_unsafe_extensions was honoured. Loaded projects now check the binary like find_virtualenvs and ignore load_unsafe_extensions.