Bump Avalonia.Themes.Fluent from 11.3.11 to 11.3.12

---
updated-dependencies:
- dependency-name: Avalonia.Themes.Fluent
  dependency-version: 11.3.12
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

ImageMerge/ImageMerge.csproj

@@ -12,7 +12,7 @@
     <ItemGroup>
         <PackageReference Include="Avalonia" Version="11.3.12"/>
         <PackageReference Include="Avalonia.Desktop" Version="11.3.12"/>
-        <PackageReference Include="Avalonia.Themes.Fluent" Version="11.3.11" />
+        <PackageReference Include="Avalonia.Themes.Fluent" Version="11.3.12" />
         <PackageReference Include="Avalonia.Fonts.Inter" Version="11.3.11" />
         <!--Condition below is needed to remove Avalonia.Diagnostics package from build output in Release configuration.-->
         <PackageReference Condition="'$(Configuration)' == 'Debug'" Include="Avalonia.Diagnostics" Version="11.3.11" />