Update broken link in the docs (#446)

docs/api/FAQ.md

@@ -55,7 +55,7 @@ The above may also apply when when you use [polkadot-js/apps](https://github.com
 
 The API itself is independent on where the signature comes from and how it is injected. Additionally it implements a signer interface, that can be used for external signing - an example of this is the [polkadot-js/apps](https://github.com/polkadot-js/apps) support for signing via extensions and even the [polkadot-js/extension](https://github.com/polkadot-js/extension) support for tools such as the [Parity Signer](https://github.com/paritytech/parity-signer).
 
-As of this writing we don't have an explicit example of implementing the signer interface in these docs, although we do use one in [our tests](https://github.com/polkadot-js/api/blob/master/packages/api/test/util/SingleAccountSigner.ts). Additionally, the [polkadot-js/tools](https://github.com/polkadot-js/tools) has an implementation of [a very basic offline signer](https://github.com/polkadot-js/tools/tree/master/packages/signer-cli) where transactions are generated in one process and signatures in another non-connected process.
+As of this writing we don't have an explicit example of implementing the signer interface in these docs, although we do use one in [our tests](https://github.com/polkadot-js/api/blob/master/packages/api/src/test/SingleAccountSigner.ts). Additionally, the [polkadot-js/tools](https://github.com/polkadot-js/tools) has an implementation of [a very basic offline signer](https://github.com/polkadot-js/tools/tree/master/packages/signer-cli) where transactions are generated in one process and signatures in another non-connected process.
 
 
 ## I would like to send a root transaction