Fix `lightning-transaction-sync` docs

[TheBlueMatt]

#4175 (comment) and bitcoindevkit/rust-electrum-client#181

[tnull]

Hopefully fixed upstream soon bitcoindevkit/rust-electrum-client#183.

[tnull]

electrum-client just did a patch release for the fix: https://crates.io/crates/electrum-client/0.24.1

Should be fixed.