AncestryDNA is making several during August 2020 to improve accuracy and validity of matches. From late August (no specific date) they will remove matches which only share 6-7.9 centimorgans because there are many matches in this range that are not valid 5-8th cousins. They could be as distant as 20th cousins. These false matches tempt us to waste time and make false conclusions, so this is a good change.
Having said that, you might have matches in this range where you actually can confirm a relationship using genealogical records or stronger matches by your closer relatives, so you might want to keep these.