build: Updating a missing workflow file `add-depr-ticket-to-depr-board.yml`.

The .github/workflows/add-depr-ticket-to-depr-board.yml workflow is missing or needs an update to stay in
sync with the current standard for this workflow as defined in the
`.github` repo of the `openedx` GitHub org.

Author: Feanil Patel

.github/workflows/add-depr-ticket-to-depr-board.yml

@@ -16,4 +16,4 @@ jobs:
     secrets:
       GITHUB_APP_ID: ${{ secrets.GRAPHQL_AUTH_APP_ID }}
       GITHUB_APP_PRIVATE_KEY: ${{ secrets.GRAPHQL_AUTH_APP_PEM }}
-      SLACK_BOT_TOKEN: ${{ secrets.SLACK_ISSUE_BOT_TOKEN }}
+      SLACK_BOT_TOKEN: ${{ secrets.SLACK_ISSUE_BOT_TOKEN }}