Update `mkTxVotingProcedures`

When multiple `L.Voter` entries exist within a voting procedure, only the first one is currently processed—all subsequent voters are ignored. Update the function signature: Modify mkTxVotingProcedures to accept a list of L.VotingProcedure (singular) rather than L.VotingProcedures if the design is intended to support only one voter per procedure.