Clarify help for loading old backups
Clarify help for loading old backups

The previous instructions from `-h` didn't make it clear that `-s` and
`-d $DIR` could be used together to load old backups.

This commit changes the help text to make that combination more obvious.

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet