--trust is too high privilege for a machine charm

[nobuto-m]

Bug Description

The document suggests to add --trust when deploying the charm.

grafana-agent-operator/README.md

Lines 36 to 40 in 49abf15

	The Grafana agent may be deployed using the juju command line:
	```bash
	juju deploy grafana-agent --trust
	```

I don't think that's a necessary privilege since grafana agent doesn't have to access to credentials of substrates. e.g. MAAS credentials.

If it's really necessary, we should add some clarifications around it.

To Reproduce

N/A - as a documentation issue

Environment

With MAAS provider in mind.

Relevant log output

N/A

Additional context

No response

[simskij]

Yes, trust is not needed for the machine subordinate. Docs need to be updated accordingly.