[docs] Suggestions for cleos set account command

[lparisc]

File: docs/02_cleos/03_command-reference/set/set-account.md

Refer users to the Accounts and Permissions protocol document to give them access to the deep descriptions of perms and auths.

File: docs/02_cleos/03_command-reference/set/set-account.md#command

Remove inaccurate comment "The set account permission command is subject to change so its associated Class is not fully documented." What is subject to change are the actual fields within the JSON input. However, this is true for all commands that pass JSON input that depend on the underlying associated class. It is probably a good idea to add a blue information callout to highlight this fact on all cleos commands that receive/pass JSON parameters to the corresponding RPC API.