Retire old description endpoint in metadata()

[juliasilge]

BTW, related to these draft names--do you think it might be time to fully retire the old V2 description endpoint in metadata()? Seems like it's a regular source of confusion because of the ways the things it returns don't necessarily match the response downloads anymore.

Originally posted by @jmobrien in #264 (comment)

I definitely think so -- great reminder 🙏

[jmobrien]

FYI, this would affect metadata(), survey_questions(), column_map(), and infer_data_types() (used for label = true in fetch_survey()), which all still use that endpoint.

[jmobrien]

Making a note - the current endpoint for fetch_survey() now has an includeLabelColumns option that could probably supersede infer_data_types()

https://api.qualtrics.com/6b00592b9c013-start-response-export

[juliasilge]

Related to #294, I don't think we can use the mock servers with this old endpoint. If we switch these over, we should be able to move all those tests away from vcr.