Bump Microsoft.Extensions.Configuration.Abstractions in /src

Bumps [Microsoft.Extensions.Configuration.Abstractions](https://github.com/dotnet/runtime) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](dotnet/runtime@v8.0.0...v9.0.0)

---
updated-dependencies:
- dependency-name: Microsoft.Extensions.Configuration.Abstractions
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

src/Mattox.NServiceBus.Tests/Mattox.NServiceBus.Tests.csproj

@@ -8,7 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="8.0.0" />
+        <PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="9.0.0" />
         <PackageReference Include="NServiceBus" Version="8.2.1" />
         <PackageReference Include="NServiceBus.Extensions.Hosting" Version="2.0.0" />
     </ItemGroup>