[Backend] Remove expired upgrade buffer

The 72 hour buffer before resetting someone's account back to the
default values after an upgrade expires is no longer necessary. Files
aren't automatically deleted once the upgrade expires, so the buffer
doesn't really serve a purpose.

backend/db/users.go

@@ -855,7 +855,7 @@ func CheckActiveUpgrades() {
 			return
 		}
 
-		if upgradeExp.Add(time.Hour * 72).Before(time.Now()) {
+		if upgradeExp.Before(time.Now()) {
 			// User doesn't have an active upgrade, set send to
 			// default amount
 			revertIDs = append(revertIDs, id)