Bump SixLabors.ImageSharp from 2.1.7 to 2.1.9 in /ImageFormats

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.7 to 2.1.9.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.7...v2.1.9)

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

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

ImageFormats/ImageFormats.csproj

@@ -29,7 +29,7 @@
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
-    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.7" />
+    <PackageReference Include="SixLabors.ImageSharp" Version="2.1.9" />
   </ItemGroup>
 
   <ItemGroup>