Patch walkers to not set user agent on wasm (#8022)

### What

This PR patches walkers to this PR:
- podusowski/walkers#222

This fixes an issue where mapbox backgrounds do not work on Safari and
Firefox (due to the requests trying to set a user agent).

### 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 the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/8022?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/8022?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
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/8022)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

Cargo.lock

@@ -8888,8 +8888,7 @@ dependencies = [
 [[package]]
 name = "walkers"
 version = "0.28.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "40c2f8ce4e3e8489bf3b75639aa26af4c3740f18b2e38ba6e90bf9468ec5eed5"
+source = "git+https://github.com/rerun-io/walkers?rev=8939cceb3fa49ca8648ee16fe1d8432f5ab0bdcc#8939cceb3fa49ca8648ee16fe1d8432f5ab0bdcc"
 dependencies = [
  "egui",
  "egui_extras",

Cargo.toml

@@ -572,6 +572,8 @@ significant_drop_tightening = "allow" # An update of parking_lot made this trigg
 
 # egui_commonmark = { git = "https://github.com/rerun-io/egui_commonmark", rev = "7a9dc755bfa351a3796274cb8ca87129b051c084" } # https://github.com/lampsitter/egui_commonmark/pull/65
 
+walkers = { git = "https://github.com/rerun-io/walkers", rev = "8939cceb3fa49ca8648ee16fe1d8432f5ab0bdcc" } # https://github.com/podusowski/walkers/pull/222
+
 # commit on `rerun-io/re_arrow2` `main` branch
 # https://github.com/rerun-io/re_arrow2/commit/e4717d6debc6d4474ec10db8f629f823f57bad07
 re_arrow2 = { git = "https://github.com/rerun-io/re_arrow2", rev = "e4717d6debc6d4474ec10db8f629f823f57bad07" }