Change casing of success status

[mitchdawson1982]

I have noticed that the preprod success slack notification isn't being triggered and I believe that it is a result of the status configuration casing.
I believe the success status needs to match notify_when: success,failure,cancelled,warnings,skipped as per if: github.event.workflow_run.conclusion == 'success'

  with:
    status: Success
    notification_title: Deployment Successful
    message_format: :rocket: <https://preprod.find-moj-data.service.justice.gov.uk/|New Preproduction Deployment>
    footer: Linked Repo <https://github.com/ministryofjustice/find-moj-data|ministryofjustice/find-moj-data> | <https://github.com/ministryofjustice/find-moj-data/actions/runs/|View>
    notify_when: success,failure,cancelled,warnings,skipped
    mention_users_when: success,failure,cancelled,warnings,skipped
    mention_groups_when: success,failure,cancelled,warnings,skipped
    icon_success: :heavy_check_mark:
    icon_failure: :x:
    icon_cancelled: :x:
    icon_warnings: :large_orange_diamond:
    icon_skipped: :fast_forward:
  env:
    SLACK_WEBHOOK_URL: ***