Update TransactionPoolRetirementCerts function and remove TransactionPoolUpdates

[ZiruiXue]

Hi team,
Could you help review below functions?
TransactionPoolUpdates(ctx context.Context, hash string) ([]TransactionPoolCert, error)
TransactionPoolUpdateCerts(ctx context.Context, hash string) ([]TransactionPoolCert, error)
TransactionPoolRetirementCerts(ctx context.Context, hash string) ([]TransactionPoolCert, error)
It seems the TransactionPoolUpdates is not in use. Could you help update the TransactionPoolRetirementCerts? It doesn't return the expect result like the blockfrost restapi.

Thanks.