Bump SixLabors.ImageSharp from 3.1.5 to 3.1.6

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 3.1.5 to 3.1.6.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v3.1.5...v3.1.6)

---
updated-dependencies:
- dependency-name: SixLabors.ImageSharp
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

SrcSet.Core/SrcSet.Core.csproj

@@ -21,7 +21,7 @@
 
 	<ItemGroup>
 		<PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="all" />
-		<PackageReference Include="SixLabors.ImageSharp" Version="3.1.5" />
+		<PackageReference Include="SixLabors.ImageSharp" Version="3.1.6" />
 		<None Include="../README.md" CopyToOutputDirectory="PreserveNewest" Pack="true" PackagePath="." />
 	</ItemGroup>
 </Project>