Docs and help out of date for commands in this repo

Example: `aio plugins update`

### Expected Behaviour

[README](https://github.com/adobe/aio-cli#aio-plugins-update) matches [source code](https://github.com/adobe/aio-cli/blob/master/src/commands/update.js#L231) in terms of description and available flags.

```
Update all installed plugins.
This command will only:
- update user-installed plugins that are not core

USAGE
$ aio plugins update [-h] [-i] [-l] [-c] [-v]

FLAGS
-h, --help Show CLI help.
-v, --verbose
-i --interactive ...
-l --list ...
-c --confirm ...

DESCRIPTION
Update all installed plugins.
This command will only:
- update user-installed plugins that are not core
```

### Actual Behaviour

Only a short description and a small subset of flags are shown:

```
Update installed plugins.

USAGE
$ aio plugins update [-h] [-v]

FLAGS
-h, --help Show CLI help.
-v, --verbose

DESCRIPTION
Update installed plugins.
```