update slack channel (#87)

Author: rscohn2

.github/workflows/slack.yaml

@@ -19,7 +19,7 @@ jobs:
       if: env.NOTIFY_SLACK == 'true'
       uses: slackapi/[email protected]
       with:
-        channel-id: "rc-test"
+        channel-id: "wg-open-source"
         slack-message: "${{ github.actor }} opened a new RFC: ${{ github.event.pull_request.title }}. URL: ${{ github.event.pull_request.html_url }}"
       env:
         SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}