Update Student State report documentation to reflect human-readable table/CSV data
With Opencraft's work on the Student State report, CSV column values are no longer in JSON but in human-readable text. Update the doc to reflect that several additional columns have also been added.
See for related doc updates:
Steps to Reproduce
Reason for Variance
User Impact Summary
This is already done. The State column remains in JSON format for backwards compatibility, but the other new columns are described accurately at https://edx.readthedocs.io/projects/edx-partner-course-staff/en/latest/student_progress/course_answers.html#report-all-learners-answer-submissions