Bump System.Drawing.Common from 8.0.20 to 8.0.21

---
updated-dependencies:
- dependency-name: System.Drawing.Common
  dependency-version: 8.0.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Directory.Packages.props

@@ -16,6 +16,6 @@
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.5" />
     <!-- After an upgrade of these libraries the nuspec file should also be updated -->
     <PackageVersion Include="Avalonia" Version="11.3.7" />
-    <PackageVersion Include="System.Drawing.Common" Version="8.0.20" />
+    <PackageVersion Include="System.Drawing.Common" Version="8.0.21" />
   </ItemGroup>
 </Project>