Extend AES key usage example list in man page

Extend the list of uses that the generated AES key serves in the man
page, from just pertaining the password safe to including OTP slots and
the encrypted volume.

Author: d-e-s-o

doc/nitrocli.1

@@ -87,7 +87,8 @@ The user PIN is reset to 123456, the admin PIN to 12345678.
 
 If the \fB\-\-only-aes-key\fR option is set, the command does not perform a
 full factory reset but only creates a new AES key.
-The AES key is for example used to encrypt the password safe.
+The AES key is for example used to encrypt the password safe, OTP slots, and
+encrypted volume.
 
 This command requires the admin PIN.
 To avoid accidental calls of this command, the user has to enter the PIN even