cleanup openapi spec across repos

[ryanwaits]

There have been a number of minor copy issues that have popped up when fetching openapi specs, need to dedicate some time to clean these up for docs automation.

[ECBSJ]

Dev suggested we give a better explanation of what the transaction_payload property should be when passing into the https://api.hiro.so/v2/fees/transaction endpoint. He stated that it wasn't clear enough.

here's more context in this Discord message.

let transaction: StacksTransactionWire
let txlength = estimateTransactionByteLength(transaction)

const json = {
  **transaction_payload: bytesToHex(serializePayloadBytes(transaction.payload)),**
  estimated_len: txlength
}

let response = await fetch("https://api.hiro.so/v2/fees/transaction", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify(json)
})
let result = await response.json()

I guess it's not obvious that one should be grabbing the payload property of the StacksTransactionWire class after it's constructed.