Bump the avalonia-core group with 1 update

Bumps Avalonia from 11.3.8 to 11.3.9

---
updated-dependencies:
- dependency-name: Avalonia
  dependency-version: 11.3.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: avalonia-core
...

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

Author: dependabot[bot]

Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
     <Nullable>enable</Nullable>
-    <AvaloniaVersion>11.3.8</AvaloniaVersion>
+    <AvaloniaVersion>11.3.9</AvaloniaVersion>
   </PropertyGroup>
 </Project>