NU1903 is logged twice

@ViktorHofer commented on [Mon, 08 Jul 2024 15:50:50 GMT](https://github.com/NuGet/Home/issues/13610)
```
C:\Users\vihofer\Downloads\testapp>..\dotnet-sdk-9.0.100-preview.7.24358.3-win-x64\dotnet.exe build
Restore succeeded with 2 warning(s) in 0.3s
C:\Users\vihofer\Downloads\testapp\testapp.csproj : warning NU1903: Package 'System.Net.Http' 4.3.0 has a known high severity vulnerability, https://github.com/advisories/GHSA-7jgj-8wvc-jh57
C:\Users\vihofer\Downloads\testapp\testapp.csproj : warning NU1903: Package 'System.Text.RegularExpressions' 4.3.0 has a known high severity vulnerability, https://github.com/advisories/GHSA-cmhx-cq75-c4mj
You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
testapp succeeded with 2 warning(s) (0.3s) → bin\Debug\netstandard1.6\testapp.dll
C:\Users\vihofer\Downloads\testapp\testapp.csproj : warning NU1903: Package 'System.Net.Http' 4.3.0 has a known high severity vulnerability, https://github.com/advisories/GHSA-7jgj-8wvc-jh57
C:\Users\vihofer\Downloads\testapp\testapp.csproj : warning NU1903: Package 'System.Text.RegularExpressions' 4.3.0 has a known high severity vulnerability, https://github.com/advisories/GHSA-cmhx-cq75-c4mj
```

I assume the warning is logged both during restore and during the build target.