Google last week announced the specific date when adsenseformobileapps.com will stop working. Until now, advertisers using Google Ads (former AdWords) could exclude app inventory by excluding this url on the targeting.
In August, Google announced the app negative targeting would be discontinued in September. And starting September 18, 2018, AdWords API requests that attempt to target or exclude a Placement criterion where the url is exactly adsenseformobileapps.com will fail and result in a CriterionError with reason INVALID_PLACEMENT_URL.
After this date it will not be possible to exclude apps on Google Ads. Google recommends to refine the app targeting and exclusions using any of the following targetings: content exclusions; device types; mobile app categories; mobile carriers; mobile platforms; placements; and verticals.