Improve Linux keyring docs

[leslie-corbalt]

I use WSL2 linux (windows subsystem linux version 2 running ubuntu 20.04). Since I don't log into linux, the gnome-keyring is locked.
To unlock it, I had to run the following 2 commands:

dbus-run-session -- bash --noprofile --norc
echo -n <sudo-password> | gnome-keyring-daemon --unlock # this creates the keyring and unlocks it

To verify the keyring exists, run

ls -al ~/.local/share/keyrings

Note: my opinion is to only allow users to configure the API option (and not use keyrings at all). A pre-requisite for using kion should be for a user to verify they have the Add App API Key in the CloudTamer UI. If not, they can write a ticket and request the API key permission.