Update Slack channel reference from g_delivery to g_release_and_deploy

Dave Smithrequested to merge
duo-edit-20251121-220226 into main

This MR updates the Slack channel reference in the Release & Deploy group handbook page from #g_delivery to #g_release_and_deploy to reflect the channel rename.

Changes:

  • Updated the Slack channel link in the Common Links table from #g_delivery to #g_release_and_deploy

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