Bump SixLabors.ImageSharp (#1975)

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.6 to 3.1.3.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.6...v3.1.3)

---
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]

examples/CSharp/OpenGL Tutorials/Tutorial 3.5 - Lighting Maps/Tutorial 3.5 - Lighting Maps.csproj

@@ -8,7 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-      <PackageReference Include="SixLabors.ImageSharp" Version="2.1.6" />
+      <PackageReference Include="SixLabors.ImageSharp" Version="3.1.3" />
     </ItemGroup>
 
     <ItemGroup>