message: rpc: document RPC_TRANSACTION_ALREADY_IN_CHAIN exception
  It is not documented that if you attempt to send a transaction
  which already exists in a block, an RPC_TRANSACTION_ALREADY_IN_CHAIN
  exception will be raised. This should be documented so that developers
  are aware that this exception is raised.
diff: @@ -807,10 +807,11 @@ static RPCHelpMan sendrawtransaction()
  {
  return RPCHelpMan{"sendrawtransaction",
  "\nSubmit a raw transaction (serialized, hex-encoded) to local node and network.\n"
  - "\nNote that the transaction will be sent unconditionally to all peers, so using this\n"
  + "\nThe transaction will be sent unconditionally to all peers, so using sendrawtransaction\n"
  "for manual rebroadcast may degrade privacy by leaking the transaction's origin, as\n"
  "nodes will normally not rebroadcast non-wallet transactions already in their mempool.\n"
  - "\nAlso see createrawtransaction and signrawtransactionwithkey calls.\n",
  + "\nA specific exception, RPC_TRANSACTION_ALREADY_IN_CHAIN, may throw if the transaction cannot be added to the mempool.\n"
  + "\nRelated RPCs: createrawtransaction, signrawtransactionwithkey\n",
  {
  {"hexstring", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The hex string of the raw transaction"},
  },
  