Bump slackapi/slack-github-action from 1.26.0 to 2.1.0 (#225)

Author: dependabot[bot]

.github/workflows/build.yml

@@ -73,7 +73,7 @@ jobs:
 
     - name: Slack notification
       id: slack
-      uses: slackapi/slack-github-action@v1.26.0
+      uses: slackapi/slack-github-action@v2.1.0
       if: ${{ github.event_name != 'pull_request' }}
       with:
         payload: |