De-race `TestExpireEDUs` (#2654)

In some conditions (fast CPUs), this test would race the clock for EDU expiration when all we want to make sure of is that the expired EDUs are properly deleted. Given this, we set the expiry time to 0 so the specified EDUs are always deleted when DeleteExpiredEDUs is called.
Fixes #2650.

Signed-off-by: Winter <winter@winter.cafe>

federationapi/storage/storage_test.go

@@ -31,7 +31,7 @@ func mustCreateFederationDatabase(t *testing.T, dbType test.DBType) (storage.Dat
 
 func TestExpireEDUs(t *testing.T) {
 	var expireEDUTypes = map[string]time.Duration{
-		gomatrixserverlib.MReceipt: time.Millisecond,
+		gomatrixserverlib.MReceipt: 0,
 	}
 
 	ctx := context.Background()