Bump slackapi/slack-github-action from 2.0.0 to 2.1.1

Bumps [slackapi/slack-github-action](https://github.com/slackapi/slack-github-action) from 2.0.0 to 2.1.1.
- [Release notes](https://github.com/slackapi/slack-github-action/releases)
- [Commits](slackapi/slack-github-action@485a9d4...91efab1)

---
updated-dependencies:
- dependency-name: slackapi/slack-github-action
  dependency-version: 2.1.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

.github/workflows/terraform.yaml

@@ -117,7 +117,7 @@ jobs:
 
     - name: Notify Slack
       if: failure()
-      uses: slackapi/slack-github-action@485a9d42d3a73031f12ec201c457e2162c45d02d # v2.0.0
+      uses: slackapi/slack-github-action@91efab103c0de0a537f72a35f6b8cda0ee76bf0a # v2.1.1
       with:
         channel-id: ${{ env.SLACK_CHANNEL }}
         slack-message: "Flightdeck acceptance terraform has failed to ${{ inputs.terraform_command }} on the ${{ inputs.module }} module."

.github/workflows/tests.yaml

@@ -75,7 +75,7 @@ jobs:
 
     - name: Notify Slack
       if: failure()
-      uses: slackapi/slack-github-action@485a9d42d3a73031f12ec201c457e2162c45d02d # v2.0.0
+      uses: slackapi/slack-github-action@91efab103c0de0a537f72a35f6b8cda0ee76bf0a # v2.1.1
       with:
         channel-id: ${{ env.SLACK_CHANNEL }}
         slack-message: "Flightdeck acceptance tests have failed on the testing cluster."