[UX] Improved formatting for release notes (#40320)

## Summary of the Pull Request

Before vs after:
![Screenshot 2025-07-01
130138](https://github.com/user-attachments/assets/f850298f-fe0b-43c1-9bae-eee712dec5e8)

## PR Checklist

- [x] **Closes:** #40319
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

src/settings-ui/Settings.UI/SettingsXAML/OOBE/Views/OobeWhatsNew.xaml.cs

@@ -112,7 +112,7 @@ namespace Microsoft.PowerToys.Settings.UI.OOBE.Views
             foreach (var release in latestReleases)
             {
                 releaseNotesHtmlBuilder.AppendLine("# " + release.Name);
-                var notes = removeHashRegex.Replace(release.ReleaseNotes, "\r\n## Highlights");
+                var notes = removeHashRegex.Replace(release.ReleaseNotes, "\r\n### Highlights");
 
                 // Add a unique counter to [github-current-release-work] to distinguish each release,
                 // since this variable is used for all latest releases when they are merged.