Bump ReportGenerator from 5.3.8 to 5.3.9

Bumps [ReportGenerator](https://github.com/danielpalme/ReportGenerator) from 5.3.8 to 5.3.9.
- [Release notes](https://github.com/danielpalme/ReportGenerator/releases)
- [Commits](danielpalme/ReportGenerator@v5.3.8...v5.3.9)

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

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

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="GitHubActionsTestLogger" Version="2.4.1" PrivateAssets="all" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
     <PackageReference Include="PublicApiGenerator" Version="11.1.0" />
-    <PackageReference Include="ReportGenerator" Version="5.3.8" PrivateAssets="all" />
+    <PackageReference Include="ReportGenerator" Version="5.3.9" PrivateAssets="all" />
     <PackageReference Include="Serilog" Version="4.0.1" />
     <PackageReference Include="Serilog.Enrichers.Environment" Version="3.0.1" />
     <PackageReference Include="Serilog.Enrichers.Thread" Version="4.0.0" />