mon: exception for dashboard in config-key warning

mon: exception for dashboard in config-key warning

This warning went in with the expectation that nobody
would be using config-key commands for modules any more,
but the dashboard does use these in order to get the
"-i" functionality on the CLI for loading certs/keys.

In Nautilus they can switch to using "-i" on real module
commands, but for Mimic let's silence the warning for
the dashboard module.

Fixes: https://tracker.ceph.com/issues/24689
Signed-off-by: John Spray <john.spray@redhat.com>