Revert #5644: dispatch nightly workflow for push-to-main integration tests

Reverts #5644, which had pointed push-to-main at the PR workflow to avoid the
full CloudSlow suite timing out. That's no longer needed: the nightly workflow
now differentiates between `integration` (full, on schedule) and
`integration-short` (on workflow_dispatch). Since this cross-org dispatch
arrives as workflow_dispatch, commits to main run `integration-short` —
CloudSlow still skips via -short, but locally-covered tests run against real
clouds, unlike the PR task's skiplocal variant.

Co-authored-by: Isaac

Author: pietern

.github/workflows/push.yml

@@ -556,15 +556,15 @@ jobs:
             -f pull_request_number=${{ github.event.pull_request.number }} \
             -f commit_sha=${{ github.event.pull_request.head.sha }}
 
-      # Use the PR workflow (which runs in short mode) so commits to main do not
-      # trigger the slow CloudSlow integration tests. Those run only on the
-      # nightly schedule (and on workflow-file changes), not on every commit.
+      # Dispatch the nightly workflow; as a workflow_dispatch event it runs
+      # integration-short (CloudSlow still skips via -short, but locally-covered
+      # tests run against real clouds, unlike the PR task's skiplocal variant).
       - name: Trigger integration tests (push to main)
         if: ${{ github.event_name == 'push' }}
         env:
           GH_TOKEN: ${{ steps.generate-token.outputs.token }}
         run: |-
-          gh workflow run cli-isolated-pr.yml -R ${{ secrets.ORG_NAME }}/${{ secrets.REPO_NAME }} \
+          gh workflow run cli-isolated-nightly.yml -R ${{ secrets.ORG_NAME }}/${{ secrets.REPO_NAME }} \
             --ref main \
             -f commit_sha=${{ github.event.after }}