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/Localisation.WPF/Localisation.WPF.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>net462;net6.0-windows;net7.0-windows</TargetFrameworks>
@@ -12,7 +12,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="System.Management" Version="7.*" />
-    <PackageReference Include="System.Reactive" Version="5.0.0" />
+    <PackageReference Include="System.Reactive" Version="6.0.0" />
   </ItemGroup>
   <ItemGroup>
     <Resource Include="Resources\UICultureIcon.ico" />