R4R: Fix failack payload

[abelliumnt]

According to our cross chain protocol, once there are panic in handling syn package in oracle app, an fail ack package will be generated. In the fail ack package, the syn payload will be write back to BSC. But the syn payload doesn't include package header. In currently implementation, the syn package header is also written back to BSC which result in BSC decoding issue. This PR will remove the syn package header before generating fail ack package.

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