fix(plasma): alt-da requires only commitments to be encoded in hexadecimal

[dndll]

Tested with copypaste of the batcher client. For Future reference: https://github.com/ethereum-optimism/specs/blob/8efc7a3fe800367bb8f407ab4fe284570a18ebc9/specs/experimental/alt-da.md?plain=1#L99-L129 Is the specification, unfortunately the batcher client expects a raw utf8 bytearray over the wire.

HTTP/1.1 200 OK
content-type: application/octet-stream
date: Wed, 10 Jul 2024 13:00:35 GMT
transfer-encoding: chunked

n[T����gL#3�Z�I'Co��JX�?�OT`�

Not a hex encoded commitment. Notably, they do encode it further downstream for the eth tx, so I wonder if they are doubling their commitment sizes if people are encoding at source and they are reencoding before sending to eth. Or perhaps I was stupid enough to be the only person who blindly followed the spec.

This change is