workflows/labels: fix stale label date sorting

                    'unmarked_as_duplicate',

                  ].includes(event))

                  .map(({ created_at, updated_at, committer, submitted_at }) => new Date(updated_at ?? created_at ?? submitted_at ?? committer.date))

                  .sort()

                  .reverse()

                  // Reverse sort by date value. The default sort() sorts by string representation, which is bad for dates.

                  .sort((a,b) => b-a)

                  .at(0) ?? item.created_at

                )