add help text for password connector flag
add help text for password connector flag

without this, the environment variable ([$CONCOURSE_PASSWORD_CONNECTOR])
doesn't appear in the help text

Signed-off-by: Aidan Oldershaw <30ef7a6e0d016bc846f26d89dacbd23aceded206@pivotal.io>
Co-authored-by: Esteban Foronda <c2ef34efb00e2335c4d8f52a0ed1c348321cd911@vmware.com>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse