Outdated interchange protocol documentation

[jorisvandenbossche]

From pandas-dev/pandas#50164 (comment)

For example, we changed the size property to be a method (#74 (comment)), but this is not reflected in the docs: https://data-apis.org/dataframe-protocol/latest/API.html

The documentation includes the full abstract interface as code block. So we should probably copy the current version to update the docs (or actually use some automatic "include code from file" sphinx feature?)

[rgommers]

Thanks @jorisvandenbossche. It looks like we should fix the deployment via CI. I'll make some time for this, there's some other housekeeping to do that I started on earlier today.