Remove validate-quick-start-module workflow and the create-issue step (#2081)

## Summary

Two cleanups to the quick start GitHub Actions workflows:

1. **Delete `validate-quick-start-module.yml`** — this validation
workflow is no longer needed here.

Validation is done here:
https://github.com/pytorch/test-infra/blob/main/.github/workflows/validate-binaries.yml
after every RC, before and after the Release

3. **Remove the "Create Issue if failed" step** from
`update-quick-start-module.yml`.

### Why remove the create-issue step

The step used `dacbd/create-issue-action@main` and passed it
`secrets.PYTORCHBOT_TOKEN`:

```yaml
- name: Create Issue if failed
  uses: dacbd/create-issue-action@main
  if: ${{ failure() }}
  with:
    token: ${{secrets.PYTORCHBOT_TOKEN}}
```

This is a supply-chain exposure:
- The action is pinned to a **mutable `@main` ref**, so any future (or
compromised) commit runs in our job.
- It receives a **long-lived broad PAT** (`PYTORCHBOT_TOKEN`), far more
privileged than opening an issue requires. A malicious version could
exfiltrate it; the `pytorchbot-env` environment gates *release* of the
secret but does not stop the third-party action from reading it once the
job runs.

Since the failure is already visible from the scheduled run's status,
the step isn't needed — removing it is the simplest fix and eliminates
the exposure. The `Create Pull Request` step is unchanged (it
legitimately needs a PAT so the PR triggers CI).

This PR was authored with the assistance of an AI coding assistant.

Author: atalman

.github/workflows/update-quick-start-module.yml

@@ -104,15 +104,6 @@ jobs:
           printf '%s\n' "$MACOS_RELEASE_MATRIX" > macos_release_matrix.json
           python3 ./scripts/gen_quick_start_module.py --autogenerate > assets/quick-start-module.js
           rm *_matrix.json
-      - name: Create Issue if failed
-        uses: dacbd/create-issue-action@main
-        if: ${{ failure() }} # only run when this job is failed.
-        with:
-          title: Updating quick start module failed
-          token: ${{secrets.PYTORCHBOT_TOKEN}}
-          assignees: ${{github.actor}}
-          labels: bug
-          body: Updating quick start module failed, please fix update quick start module
       - name: Create Pull Request
         uses: peter-evans/create-pull-request@v3
         with: