src: document newer values for --unhandled-rejections flag
These values were added in v15.0.0 by #33475 but were not included in the
node --help
output.
Also document which value is the default.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
These values were added in v15.0.0 by #33475 but were not included in the
node --help
output.
Also document which value is the default.