publish-nightly failures

[timcassell]

error: Response status code does not indicate success: 413 (The total packages size for the pending uploads is too large. The feed owner may have to upgrade the MyGet subscription to resolve this issue.).

https://github.com/dotnet/BenchmarkDotNet/actions/runs/15668719450

[AndreyAkinshin]

It's fixed: https://github.com/dotnet/BenchmarkDotNet/actions/runs/15678327067. I've removed all the old nightly versions except for the latest ones. Now we have enough quota to keep all the new packages. Additionally, I set up the retention rule, so we shouldn't encounter this problem in the future.