MESH-2092 Bump slackapi/slack-github-action in the dependencies group

Bumps the dependencies group with 1 update: [slackapi/slack-github-action](https://github.com/slackapi/slack-github-action).


Updates `slackapi/slack-github-action` from 2.1.1 to 3.0.1
- [Release notes](https://github.com/slackapi/slack-github-action/releases)
- [Commits](slackapi/slack-github-action@91efab1...af78098)

---
updated-dependencies:
- dependency-name: slackapi/slack-github-action
  dependency-version: 3.0.1
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/pull-request.yml

@@ -321,7 +321,7 @@ jobs:
     if: ${{ always() && github.repository == 'NHSDigital/mesh-sandbox' && github.actor== 'dependabot[bot]' && contains(needs.*.result, 'failure') }}
     steps:
       - name: Slack Notification
-        uses: slackapi/slack-github-action@91efab103c0de0a537f72a35f6b8cda0ee76bf0a
+        uses: slackapi/slack-github-action@af78098f536edbc4de71162a307590698245be95
         with:
           webhook: ${{ secrets.DEPENDABOT_SLACK_WEBHOOK_URL }}
           webhook-type: incoming-webhook