CmdPal: Remove workaround for FontIconSource.CreateIconElement (#45790)

## Summary of the Pull Request

This PR removes workaround for FontIconSource.CreateIconElement icon not
being visible, as it looks like it was fixed in WASDK 1.8.4.

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## PR Checklist

- [x] Closes: #45788
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- [ ] **Tests:** Added/updated and all pass
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- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
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- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
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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/Controls/IconBox.cs

@@ -182,25 +182,14 @@ public partial class IconBox : ContentControl
                 break;
             case FontIconSource fontIcon:
                 self.UpdateLastFontSize();
+                fontIcon.FontSize = self._lastFontSize;
                 if (self.Content is IconSourceElement iconSourceElement)
                 {
-                    fontIcon.FontSize = self._lastFontSize;
                     iconSourceElement.IconSource = fontIcon;
                 }
                 else
                 {
-                    fontIcon.FontSize = self._lastFontSize;
+                    self.Content = fontIcon.CreateIconElement();
-
-                    // For inexplicable reasons, FontIconSource.CreateIconElement
-                    // doesn't work, so do it ourselves
-                    // TODO: File platform bug?
-                    IconSourceElement elem = new()
-                    {
-                        HorizontalAlignment = HorizontalAlignment.Center,
-                        VerticalAlignment = VerticalAlignment.Center,
-                        IconSource = fontIcon,
-                    };
-                    self.Content = elem;
                 }
 
                 self.UpdatePaddingForFontIcon();