Re-generate TicketBroker binding to include named structs

[yondonfu]

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At the moment, the TicketBroker contract binding does not support named structs because the version of abigen used to generate the binding did not support using internalType information from a contract's ABI and as a result could not use the name of a Solidity struct as the name for the corresponding Go struct.

An abigen PR was just merged that adds support for using the internalType information from a contract's ABI to generate a binding that includes named structs.

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Re-generate the TicketBroker binding in eth/contracts/ticketBroker.go using the latest version of abigen. This should also allow us to remove the custom code in client.GetSenderInfo() - instead, we can directly call TicketBrokerSession.GetSenderInfo().