Common matching logic doesn't exclude expired impressions #185
Description
From https://w3c.github.io/ppa/#impression-store-maintenance:
It is not necessary to remove impressions immediately upon expiry, as long as measureConversion() excludes expired impressions from attribution. However, the user agent should not retain expired impressions indefinitely.
But the measureConversion algorithm, and in particular its common matching logic sub-algorithm, do not inspect the lifetime field.