dotnet pack fails with "Duplicate 'PackageDownload' items found" when using EnablePackageValidation with PackageValidationBaselineVersion

### Describe the bug
When I add both `PackageValidationBaselineVersion` and `EnablePackageValidation` to my project, `dotnet pack` fails:

```
/home/pavel/w/ignite-3/modules/platforms/dotnet/Apache.Ignite/Apache.Ignite.csproj : error NU1505: Warning As Error: Duplicate 'PackageDownload' items found. Remove the duplicate items or use the Update functionality to ensure a consistent restore behavior. The duplicate 'PackageDownload' items are: Apache.Ignite [3.0.0], Apache.Ignite [3.0.0].

Restore failed with 1 error(s) in 0.2s
```

### To Reproduce
```bash
git clone https://github.com/ptupitsyn/ignite-3.git -b nuget-validation-bug
cd ignite-3/modules/platforms/dotnet/Apache.Ignite
dotnet pack
```

PR with one-line change that breaks the `pack` in Apache Ignite: https://github.com/apache/ignite-3/pull/6176

### Further technical details
`dotnet --info`:

```
.NET SDK:
Version: 8.0.411
Commit: f97ff31961
Workload version: 8.0.400-manifests.ee7a832d
MSBuild version: 17.11.31+933b72e36

Runtime Environment:
OS Name: ubuntu
OS Version: 22.04
OS Platform: Linux
RID: linux-x64
Base Path: /usr/share/dotnet/sdk/8.0.411/

.NET workloads installed:
Configured to use loose manifests when installing new manifests.
There are no installed workloads to display.

Host:
Version: 9.0.4
Architecture: x64
Commit: f57e6dc747

.NET SDKs installed:
6.0.428 [/usr/share/dotnet/sdk]
7.0.410 [/usr/share/dotnet/sdk]
8.0.411 [/usr/share/dotnet/sdk]
9.0.203 [/usr/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.36 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.17 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.4 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.36 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.17 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.4 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
None

Environment variables:
Not set

global.json file:
/home/pavel/w/tests/delme123/ignite-3/modules/platforms/dotnet/global.json
```