CmdPal: make spacing in gallery view uniform (#44542)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request

This PR ensures the spacing between items in the gallery view is
consistent both vertically and horizontally.

<img width="823" height="599" alt="image"
src="https://github.com/user-attachments/assets/0a2349fa-9c88-4606-82b3-94c21ad37871"
/>


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## PR Checklist

- [x] Closes: #44612
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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

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/ExtViews/ListPage.xaml

@@ -477,7 +477,10 @@
                             SelectionChanged="Items_SelectionChanged">
                             <GridView.ItemsPanel>
                                 <ItemsPanelTemplate>
-                                    <cpcontrols:WrapPanel HorizontalSpacing="8" Orientation="Horizontal" />
+                                    <cpcontrols:WrapPanel
+                                        HorizontalSpacing="8"
+                                        Orientation="Horizontal"
+                                        VerticalSpacing="8" />
                                 </ItemsPanelTemplate>
                             </GridView.ItemsPanel>
                             <GridView.ItemContainerTransitions>