Bump xunit from 2.6.2 to 2.6.4 in /TeachingRecordSystem

Bumps [xunit](https://github.com/xunit/xunit) from 2.6.2 to 2.6.4.
- [Commits](xunit/xunit@2.6.2...2.6.4)

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

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

TeachingRecordSystem/Directory.Packages.props

@@ -81,8 +81,8 @@
     <PackageVersion Include="System.Linq.Async" Version="6.0.1" />
     <PackageVersion Include="System.Net.Http.Json" Version="8.0.0" />
     <PackageVersion Include="System.Reactive" Version="6.0.0" />
-    <PackageVersion Include="xunit" Version="2.6.2" />
-    <PackageVersion Include="xunit.assert" Version="2.6.3" />
+    <PackageVersion Include="xunit" Version="2.6.4" />
+    <PackageVersion Include="xunit.assert" Version="2.6.4" />
     <PackageVersion Include="Xunit.DependencyInjection" Version="8.9.0" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.5" />
   </ItemGroup>