Bump Avalonia and Avalonia.Themes.Fluent

Bumps [Avalonia](https://github.com/AvaloniaUI/Avalonia) and [Avalonia.Themes.Fluent](https://github.com/AvaloniaUI/Avalonia). These dependencies needed to be updated together.

Updates `Avalonia` from 11.2.7 to 11.2.8
- [Release notes](https://github.com/AvaloniaUI/Avalonia/releases)
- [Commits](AvaloniaUI/Avalonia@11.2.7...11.2.8)

Updates `Avalonia.Themes.Fluent` from 11.2.4 to 11.2.8
- [Release notes](https://github.com/AvaloniaUI/Avalonia/releases)
- [Commits](AvaloniaUI/Avalonia@11.2.4...11.2.8)

---
updated-dependencies:
- dependency-name: Avalonia
  dependency-version: 11.2.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Avalonia.Themes.Fluent
  dependency-version: 11.2.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

ImageMerge/ImageMerge.csproj

@@ -10,9 +10,9 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Avalonia" Version="11.2.7"/>
+        <PackageReference Include="Avalonia" Version="11.2.8"/>
         <PackageReference Include="Avalonia.Desktop" Version="11.2.5"/>
-        <PackageReference Include="Avalonia.Themes.Fluent" Version="11.2.4"/>
+        <PackageReference Include="Avalonia.Themes.Fluent" Version="11.2.8"/>
         <PackageReference Include="Avalonia.Fonts.Inter" Version="11.2.6"/>
         <!--Condition below is needed to remove Avalonia.Diagnostics package from build output in Release configuration.-->
         <PackageReference Condition="'$(Configuration)' == 'Debug'" Include="Avalonia.Diagnostics" Version="11.2.6"/>