[atlas] Small upcoming change in measurement metadata daily dumps

Hello, We plan to make a small change in the measurement metadata daily dumps available at https://ftp.ripe.net/ripe/atlas/measurements/. Up until now these files contain the "current working set" which is defined as any measurement that runs right now or has been running in the past 14 days. (This also means that there's considerable overlap between today's and yesterday's dump.) We'll shorten this period to 7 days in early February. This has zero effect on the vast majority of our users. Those who periodically download and use these files with lower than 7 day frequency will need to update their scripts accordingly. Regards, Robert Kisteleki for RIPE Atlas team