See #949, I think we've decided this is not necessary

@larsoner as a user I think it would be a lot more convenient to have this as an option in conf.py rather than having to make custom css rules to hide the buttons. Especially as that would eliminate the need for uploading the _downloads folder to my host (this PR should probably make sure that folder does not be generated in the first place).

@lucyleeow WDYT?

I understand it would be easier to users but I am reluctant to add to our already large list of config options (though it probably doesn't add much maintenance).
How about adding a part to our documentation about how to hide this via CSS? Maybe expanding the section 'And some things can be tweaked directly in CSS:' (here). I vaguely recall a few issues about other things that can be tweaked via CSS.

Actually I hadn't considered the fact that we could avoid generating a bunch of files in the first place by having this as a config option... that might make it worth having over just a CSS trick. In MNE-Python for example I would probably turn this on for PRs to reduce Artifact upload time on CircleCI (which could also be done by some code plus CSS but it's a pain)... @lucyleeow WDYT?