Bump SixLabors.ImageSharp from 3.1.8 to 3.1.9 (#657)

---
updated-dependencies:
- dependency-name: SixLabors.ImageSharp
  dependency-version: 3.1.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/Directory.Packages.props

@@ -9,7 +9,7 @@
     <PackageVersion Include="NUnit" Version="4.3.2" />
     <PackageVersion Include="NUnit3TestAdapter" Version="5.0.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.155" />
-    <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.8" />
+    <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.9" />
     <PackageVersion Include="Verify" Version="30.3.1" />
     <PackageVersion Include="Verify.DiffPlex" Version="3.1.2" />
     <PackageVersion Include="Verify.Nunit" Version="30.3.1" />