Files are not properly deleted from GitHub Pages

[17cupsofcoffee]

I noticed after reverting a change for #912 that when a file is removed from the Zola output, it doesn't get deleted from the master branch - this means that the removed content remains accessible on the site.

For example, I reverted the publishing of newsletter 30 to give people more time to submit, but the HTML for it is still accessible if you have a direct link.

This is apparently an issue with the GitHub action we're using to publish: crazy-max/ghaction-github-pages#153

Is there any reason for us to keep keep_history set to true (the default is false)? We have the history for the site on the source branch and never directly interact with master, so not sure if there's value in having a full history there rather than just having it force pushed every time.

[ozkriff]

Originally, I enabled keep_history so it'd be easier to double-check the actual changes in Zola's output (I had a couple of issues with my own blog and early Zola). But it seems like Zola has been behaving well for quite some time now, so I don't mind disabling keep_history.