Sort 2021 events in reverse chronological order

[emaste]

Summary

Per comment in the file "Sort events by start date, with more recent events earlier in the file."

[lwhsu]

I found that all website/data/en/events/events*.toml have entries in chronological order.
Need to check if changing this affect the display in events block of https://www.freebsd.org and https://www.freebsd.org/events/

[emaste]

afaict it's ok, but we should update all of them, or change the comments

[ceri]

I committed the reverse of this in c603905d8303ee561fa8c7f10b2c6b170d017ce2 as it was more consistent with the other files.