Auto approve workflow runs (part 2) (#3886)

### What

The workflow ran into a strange issue with installing Python
dependencies.

- Set python version to `3.x`
- Event name for `pull_request_target` is not `pull_request`

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested [demo.rerun.io](https://demo.rerun.io/pr/{{
pr.number }}) (if applicable)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG

- [PR Build Summary](https://build.rerun.io/pr/{{ pr.number }})
- [Docs preview](https://rerun.io/preview/{{ pr.commit }}/docs)
<!--DOCS-PREVIEW-->
- [Examples preview](https://rerun.io/preview/{{ pr.commit }}/examples)
<!--EXAMPLES-PREVIEW-->
- [Recent benchmark results](https://ref.rerun.io/dev/bench/)
- [Wasm size tracking](https://ref.rerun.io/dev/sizes/)

.github/workflows/auto_approve.yml

@@ -12,13 +12,15 @@ jobs:
   approve-workflow-runs:
     name: "Check for approval"
     runs-on: ubuntu-latest
-    if: ${{ github.event_name == 'pull_request' || github.event.issue.pull_request }}
+    if: ${{ github.event_name == 'pull_request_target' || github.event.issue.pull_request }}
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
       - name: Setup Python
         uses: actions/setup-python@v4
+        with:
+          python-version: 3.x
 
       - name: Install dependencies
         run: |
@@ -27,7 +29,7 @@ jobs:
       - name: Wait a few seconds
         run: |
           # Give GitHub a bit of time to synchronize everything
-          sleep 10s
+          sleep 5s
 
       - name: Approve workflow runs
         run: |