Update subkey README.md (paritytech#14552)

* Update `subkey` README.md

getsubstrate.io is not maintained.

Perhaps other things should be updated here in this PR too - open to suggestions!

* Update README.md

bin/utils/subkey/README.md

@@ -25,10 +25,9 @@ You will need to have the Substrate build dependencies to install Subkey. Use th
 Command:
 
 ```bash
-# Use the `--fast` flag to get the dependencies without needing to install the Substrate and Subkey binary
-curl https://getsubstrate.io -sSf | bash -s -- --fast
 # Install only `subkey`, at a specific version of the subkey crate
 cargo install --force subkey --git https://github.com/paritytech/substrate --version <SET VERSION> --locked
+# If you run into issues building, you likely are missing deps defined in https://docs.substrate.io/install/
 ```
 
 ### Run in a container
@@ -69,7 +68,7 @@ The output above also show the **public key** and the **Account ID**. Those are
 
 The **SS58 address** (or **Public Address**) of a new account is a reprensentation of the public keys of an account for a given network (for instance Kusama or Polkadot).
 
-You can read more about the SS58 format in the [Substrate Docs](https://docs.substrate.io/v3/advanced/ss58/) and see the list of reserved prefixes in the [SS58 Registry](https://github.com/paritytech/ss58-registry).
+You can read more about the [SS58 format in the Substrate Docs](https://docs.substrate.io/reference/address-formats/) and see the list of reserved prefixes in the [SS58 Registry](https://github.com/paritytech/ss58-registry).
 
 For instance, considering the previous seed `0xa05c75731970cc7868a2fb7cb577353cd5b31f62dccced92c441acd8fee0c92d` the SS58 addresses are: