Bump System.Reactive.Linq from 5.0.0 to 6.0.0

Bumps [System.Reactive.Linq](https://github.com/dotnet/reactive) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](https://github.com/dotnet/reactive/commits)

---
updated-dependencies:
- dependency-name: System.Reactive.Linq
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

IDisposableAnalyzers.Test/IDisposableAnalyzers.Test.csproj

@@ -44,7 +44,7 @@
     <PackageReference Include="NUnit" Version="3.13.3" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.4.2" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.435" PrivateAssets="all" />
-    <PackageReference Include="System.Reactive.Linq" Version="5.0.0" />
+    <PackageReference Include="System.Reactive.Linq" Version="6.0.0" />
     <PackageReference Include="reactiveui" Version="18.4.34" />
   </ItemGroup>
 </Project>

ValidCode/ValidCode.csproj

@@ -26,7 +26,7 @@
     <PackageReference Include="Moq" Version="4.18.4" />
     <PackageReference Include="Ninject" Version="3.3.6" />
     <PackageReference Include="NUnit" Version="3.13.3" />
-    <PackageReference Include="System.Reactive.Linq" Version="5.0.0" />
+    <PackageReference Include="System.Reactive.Linq" Version="6.0.0" />
     <PackageReference Include="reactiveui" Version="18.4.34" />
   </ItemGroup>
 </Project>