api: remove create from auth-tokens help (#3341)

The auth-tokens help command included a reference to
a non-existent auth-tokens create command. Replace the
default help and also add a helpful pointer to the authenticate
command.

api/authtokens/authtokens.gen.go

@@ -44,7 +44,6 @@ func (n AuthTokenReadResult) GetResponse() *api.Response {
 	return n.response
 }
 
-type AuthTokenCreateResult = AuthTokenReadResult
 type AuthTokenUpdateResult = AuthTokenReadResult
 
 type AuthTokenDeleteResult struct {