Bump SixLabors.ImageSharp in /c_sharp/image_classification (#488)

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.1 to 2.1.9.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.1...v2.1.9)

---
updated-dependencies:
- dependency-name: SixLabors.ImageSharp
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

c_sharp/image_classification/image_classification.csproj

@@ -8,7 +8,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.ML.OnnxRuntime" Version="1.16.0" />
     <PackageReference Include="Microsoft.ML.OnnxRuntime.Managed" Version="1.16.0" />
-    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.1" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.9" />
   </ItemGroup>
 
 </Project>