Pass webhook secrets for deploy workflow

The re-usable deploy workflow has been updated to send a webhook to trigger the
update-image-tag Argo Workflow, instead of updating the govuk-helm-charts repo
directly. The deploy workflow needs the secrets for the webhook token and url,
which are stored as GitHub Organisation secrets.

.github/workflows/ci.yaml

@@ -23,4 +23,5 @@ jobs:
     needs: build-and-publish-image
     uses: alphagov/govuk-infrastructure/.github/workflows/deploy.yaml@main
     secrets:
-      GOVUK_CI_GITHUB_API_TOKEN: ${{ secrets.GOVUK_CI_GITHUB_API_TOKEN }}
+      WEBHOOK_TOKEN: ${{ secrets.ARGO_EVENTS_WEBHOOK_TOKEN }}
+      WEBHOOK_URL: ${{ secrets.ARGO_EVENTS_WEBHOOK_URL }}