events: update note, we missed two summits

Events are organized to exchange ideas about reproducible builds, get a better

understanding or cooperate on improving code or specifications. (Due to the

unprecedented events of 2020, there was no in-person event during that year.)

unprecedented events of 2020 and following, there were no in-person events during two years.)

{% assign sorted_events = site.events | sort: 'event_date' | reverse %}

{% for page in sorted_events %}