Change "transfer" extrinsics to "transfer_allow_death"

[laboon]

As transfer is deprecated on Polkadot and Kusama, it makes sense to use transfer_allow_death (or transfer_keep_alive) instead.

An example of using "transfer" is here: https://polkadot.js.org/docs/api/start/api.tx/ but I did not search through the entire repo for other examples of it.

[sibelly]

Example:

const txHash = await api.tx.balances
  .transferKeepAlive(ADDR2, 1)
  .signAndSend(ADDR1);