Bump System.Reactive from 5.0.0 to 6.0.0

Bumps [System.Reactive](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
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

src/S7PlcRx/S7PlcRx.csproj

@@ -7,7 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="System.Reactive" Version="5.0.0" />
+    <PackageReference Include="System.Reactive" Version="6.0.0" />
   </ItemGroup>
 
 </Project>