[Harmony: Enhancements] Drop digital release dates when too early

[YoGo9]

Just an idea and I'm not even sure what the cut off date should be. It will make it easier for all those releases that where released in the 90's or in the early 2000's Instead of having to delete each time the dates in the seeder.

[chaban-mb]

Related Harmony issue:

• Don't seed the release date if it's before the source service existed kellnerd/harmony#101