Bump rtCamp/action-slack-notify from 2.1.0 to 2.2.0 (#1375)

Bumps [rtCamp/action-slack-notify](https://github.com/rtCamp/action-slack-notify) from 2.1.0 to 2.2.0.
- [Release notes](https://github.com/rtCamp/action-slack-notify/releases)
- [Commits](rtCamp/action-slack-notify@v2.1.0...v2.2.0)

---
updated-dependencies:
- dependency-name: rtCamp/action-slack-notify
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/check-certificates.yml

@@ -56,7 +56,7 @@ jobs:
       # See: https://github.com/rtCamp/action-slack-notify
       - name: Slack notification of certificate verification failure
         if: failure()
-        uses: rtCamp/action-slack-notify@v2.1.0
+        uses: rtCamp/action-slack-notify@v2.2.0
         env:
           SLACK_WEBHOOK: ${{ secrets.TEAM_TOOLING_CHANNEL_SLACK_WEBHOOK }}
           SLACK_MESSAGE: |
@@ -110,7 +110,7 @@ jobs:
       - name: Slack notification of pending certificate expiration
         # Don't send spurious expiration notification if verification fails
         if: failure() && steps.check-expiration.outcome == 'failure'
-        uses: rtCamp/action-slack-notify@v2.1.0
+        uses: rtCamp/action-slack-notify@v2.2.0
         env:
           SLACK_WEBHOOK: ${{ secrets.TEAM_TOOLING_CHANNEL_SLACK_WEBHOOK }}
           SLACK_MESSAGE: |