Past events page should be reverse-chronological

[SethTisue]

https://www.scala-lang.org/pastevents/

instead of 2010 at the top, 2024 should be at the top. this is a suggestion from @darjutak that I agree with. the past-events page isn't all that prominent of course, but it's going to get a visibility bump when we link to the events page from a forthcoming blog post

@Philippus you've given that page some love over the years, is this a task that would interest you? if not, I can handle it

[Philippus]

Makes sense, I can have a look.