ShardIDFromKey still return 4 shards when starting from 0

[sophoah]

Describe the bug

When the node start from 0, HIP30 epoch hasn't been reached yet and the function below will still return shard 2 or 3 instead of 0 or 1

// ShardIDFromKey returns the shard ID statically determined from the input key
func (conf *ConfigType) ShardIDFromKey(key *bls_core.PublicKey) (uint32, error) {
	var pubKey bls.SerializedPublicKey
	if err := pubKey.FromLibBLSPublicKey(key); err != nil {
		return 0, errors.Wrapf(err,
			"cannot convert libbls public key %s to internal form",
			key.SerializeToHexStr())
	}
	epoch := conf.networkType.ChainConfig().StakingEpoch
	numShards := conf.shardingSchedule.InstanceForEpoch(epoch).NumShards()
	shardID := new(big.Int).Mod(pubKey.Big(), big.NewInt(int64(numShards)))
	return uint32(shardID.Uint64()), nil
}

What to expect
The shard belonging should be dependent on the latest epoch activation despite where the node has synced so far