build(deps): bump slackapi/slack-github-action from 1.19.0 to 1.21.0 (h…

…ashicorp#1019)

Bumps [slackapi/slack-github-action](https://github.com/slackapi/slack-github-action) from 1.19.0 to 1.21.0.
- [Release notes](https://github.com/slackapi/slack-github-action/releases)
- [Commits](slackapi/slack-github-action@v1.19.0...v1.21.0)

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

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

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

.github/workflows/benchmarks.yml

@@ -80,7 +80,7 @@ jobs:
       -
         name: Send failures to Slack
         if: ${{ failure() && !cancelled() }}
-        uses: slackapi/slack-github-action@v1.19.0
+        uses: slackapi/slack-github-action@v1.21.0
         with:
           payload: |
             {