CmdPal: Remove subtitle from all built-in top level commands (#44621)

## Summary of the Pull Request

This PR removes subtitles from all built-in top-level commands, except
for fallbacks, apps, and bookmarks.

<img width="885" height="987" alt="image"
src="https://github.com/user-attachments/assets/4da7377d-2c86-4658-a96b-33a881333639"
/>

<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [ ] Closes: #xxx
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **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

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Commands/BuiltInsCommandProvider.cs

@@ -21,7 +21,7 @@ public sealed partial class BuiltInsCommandProvider : CommandProvider
     public override ICommandItem[] TopLevelCommands() =>
         [
             new CommandItem(openSettings) { },
-            new CommandItem(_newExtension) { Title = _newExtension.Title, Subtitle = Properties.Resources.builtin_new_extension_subtitle },
+            new CommandItem(_newExtension) { Title = _newExtension.Title },
         ];
 
     public override IFallbackCommandItem[] FallbackCommands() =>