guides/user: improve copy retrieving DID and NID — radicle.xyz

The command for getting the NID was successfully updated. However, the copy did not quite match up and implied that rad self contained information about the NID.

The copy is improved to be clear about which commands are required for which information.

 > We are in the process of designing and implementing this functionality.
 If you forget your DID or NID, you can query your full identity by running `rad
 self` or alternatively you can grab your DID with `rad self --did` and your NID
 with `rad node status --only nid`.
 If you forget your DID, you can query your full identity by running `rad
 self` or alternatively you can grab your DID with `rad self --did`.
 If you need your NID, you can query for it with `rad node status --only nid`.
 ```
 $ rad self

 └╴Node          /home/paxel/.radicle/node
 ```
 This displays your alias, DID, Node ID, SSH agent status, SSH keys, and the
 locations of important files or directories.
 This displays your alias, DID, SSH agent status, SSH keys, and the locations of
 important files or directories.
 ```
 $ rad self --did
 did:key:z6Mkhp7VUnuufpvuQ3PdysShAjL86VDRUpPpkesqiysDBGs9
 ```
 For focusing on your DID.
 ```
 $ rad node status --only nid
 z6Mkhp7VUnuufpvuQ3PdysShAjL86VDRUpPpkesqiysDBGs9
 ```
 For getting the NID of the current, running node.
 > 👾
 >