build: update slackapi/slack-github-action digest to 47b1876 (#31070)

See associated pull request for more information.

Author: angular-robot

.github/actions/slack/action.yml

@@ -12,7 +12,7 @@ runs:
   using: 'composite'
   steps:
     - name: Notify about failed test
-      uses: slackapi/slack-github-action@e28cf165c92ffef168d23c5c9000cffc8a25e117 # v=v1.24.0
+      uses: slackapi/slack-github-action@47b1876080be991b1fc5ff91d384d0042e769e4e # v=v1.24.0
       with:
         channel-id: 'C015EBF2XB6'
         slack-message: '${{ inputs.JOB_NAME }} job failed for ${{ github.base_ref }} branch failed on build ${{ github.event.after }}: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}'