Bump SixLabors.ImageSharp from 2.1.7 to 2.1.8

Bumps [SixLabors.ImageSharp](https://github.com/SixLabors/ImageSharp) from 2.1.7 to 2.1.8.
- [Release notes](https://github.com/SixLabors/ImageSharp/releases)
- [Commits](SixLabors/ImageSharp@v2.1.7...v2.1.8)

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

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

OpenXmlPowerTools/OpenXmlPowerTools.csproj

@@ -48,7 +48,7 @@
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
 		</PackageReference>
 		<PackageReference Include="SixLabors.Fonts" Version="1.0.1" />
-		<PackageReference Include="SixLabors.ImageSharp" Version="2.1.7" />
+		<PackageReference Include="SixLabors.ImageSharp" Version="2.1.8" />
 		<PackageReference Include="SonarAnalyzer.CSharp" Version="9.7.0.75501">
 			<PrivateAssets>all</PrivateAssets>
 			<IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>