Bump SixLabors.ImageSharp from 2.1.3 to 3.0.1

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.3 to 3.0.1.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.3...v3.0.1)

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

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

source/POI.DiscordDotNet/POI.DiscordDotNet.csproj

@@ -28,7 +28,7 @@
         <PackageReference Include="Serilog.Sinks.Async" Version="1.5.0" />
         <PackageReference Include="Serilog.Sinks.Console" Version="4.1.1-dev-00917" />
         <PackageReference Include="Serilog.Sinks.File" Version="5.0.1-dev-00947" />
-        <PackageReference Include="SixLabors.ImageSharp" Version="2.1.5" />
+        <PackageReference Include="SixLabors.ImageSharp" Version="3.0.1" />
         <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="1.0.0-beta15" />
     </ItemGroup>