onboarding CLI: fix flux private key password

[waleedhammam]

Closes #3663

What changed?

• Update private key password flag according to flux

  # Run bootstrap for a Git repository with a passwordless private key
  flux bootstrap git --url=ssh://[email protected]/repository.git --private-key-file=<path/to/private.key> --path=clusters/my-cluster

  # Run bootstrap for a Git repository with a private key and password
  flux bootstrap git --url=ssh://[email protected]/repository.git --private-key-file=<path/to/private.key> --password=<password> --path=clusters/my-cluster

Why was this change made?

How was this change implemented?

• change flag --gpg-passphrase to use password --password in bootstrap CLI flux

How did you validate the change?

• Explain how a reviewer can verify the change themselves
  Start interactive installation with ssh repo URL / Non-interactive with passing ssh creds

go run main.go bootstrap  --private-key=<path> --private-key-password=<password>

• Integration tests -- what is covered, what cannot be covered;
  or, explain why there are no new tests

ran the acceptance test

• Unit tests -- what is covered, what cannot be covered; are
  there tests that fail without the change?

couldn't be tested with unit test as it includes running flux binary / requires git creds

Release notes

Documentation Changes

Other follow ups

[enekofb]

please share a bit of the background around the library change ... just thinking in terms of version compatibility

also please add to the PR the validation done

[waleedhammam]

@enekofb updated and tested acceptance test case