MAINT: systematically switch out `doctest-remote-data` with `doctest-remote-data-all`

`doctest-remote-data-all ` has been added to pytest-doctestplus 1.4, but also more recent releases fixed a couple of more corner cases. So if we are OK with requiring a rather new doctestplus version, we could ditch all `doctest-remote-data` directives from the docs files in exchange of just one line at the top.

This would mean testing anything in the file would require remote-data access, but in practice I think we are already doing that as only a very small amount of docs examples can run without reaching out to a service.

Inspect the documentation files for `doctest-remote-data` directives and check the project's pytest-doctestplus version requirement. Replace the individual directives with the single `doctest-remote-data-all` line where appropriate, then verify that the documentation examples still run with remote-data access.

Written by the indexing model from the issue text.