Update Postgres standby reboot reason
Update Postgres standby reboot reason

The backups actually come from the primary makeing the previous message
a bit confusing. However, the standby is still not safe to reboot
because apps read from the standby directly.

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