Brute-force silence the spurious walkers error at shutdown (#8078)

### What

Short-term workaround for
podusowski/walkers#224

Should be reverted ASAP:
- #8077

### Checklist
* [x] I have read and agree to [Contributor
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* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/8078?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/8078?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
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usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/8078)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

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crates/utils/re_log/src/lib.rs

@@ -112,6 +112,9 @@ pub fn default_log_filter() -> String {
         }
     }
 
+    //TODO(#8077): should be removed as soon as the upstream issue is resolved
+    rust_log += ",walkers::download=off";
+
     rust_log
 }