Bump NunitXml.TestLogger from 3.1.15 to 3.1.20

Bumps [NunitXml.TestLogger](https://github.com/spekt/nunit.testlogger) from 3.1.15 to 3.1.20.
- [Release notes](https://github.com/spekt/nunit.testlogger/releases)
- [Changelog](https://github.com/spekt/nunit.testlogger/blob/master/CHANGELOG.md)
- [Commits](spekt/nunit.testlogger@v3.1.15...v3.1.20)

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

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

Gu.Wpf.UiAutomation.Tests/Gu.Wpf.UiAutomation.Tests.csproj

@@ -24,7 +24,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="NUnit" Version="4.0.1" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" PrivateAssets="all" />
-    <PackageReference Include="NunitXml.TestLogger" Version="3.1.15" PrivateAssets="all" />
+    <PackageReference Include="NunitXml.TestLogger" Version="3.1.20" PrivateAssets="all" />
     <PackageReference Include="ReflectionAnalyzers" Version="0.3.1" PrivateAssets="all" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.556" PrivateAssets="all" />
   </ItemGroup>