Running microbenchmarks fail with error NU1605

Simply following instructions in https://github.com/dotnet/performance/blob/main/docs/prerequisites.md (and that used to work couple month ago)

```
vsadov@vsadovAMD2:~/perf/performance/src/benchmarks/micro$ ~/dotnet11/dotnet run -c Release -f net11.0 --cli ~/dotnet11/dotnet --filter 'System.Buffers.Tests.RentReturnArrayPoolTests.ProducerConsumer' --coreRun ~/dotnet001/runtime/artifacts/bin/testhost/net11.0-linux-Release-x64/shared/Microsoft.NETCore.App/11.0.0/corerun
/home/vsadov/perf/performance/src/benchmarks/micro/MicroBenchmarks.csproj : error NU1605:
Warning As Error: Detected package downgrade: System.Collections.Immutable from 9.0.0 to 8.0.0. Reference the package directly from the project to select a different version.
MicroBenchmarks -> BenchmarkDotNet.Extensions -> BenchmarkDotNet 0.16.0-nightly.20260320.467 -> Microsoft.CodeAnalysis.CSharp 5.0.0 -> System.Collections.Immutable (>= 9.0.0)
MicroBenchmarks -> System.Collections.Immutable (>= 8.0.0-0)

```

This is on Linux. Not sure if Windows has the same issues.

the `~/dotnet11` contains a fairly recent SDK build copy-installed.