[build] remove darc dependency for System.IO.Hashing

[jonathanpeppers]

Maestro is currently failing to open new PRs due to:

> darc update-dependencies --id 169161
Looking up build with BAR id 169161
Updating 'Microsoft.Dotnet.Sdk.Internal': '8.0.100-preview.3.23128.1' => '8.0.100-preview.3.23153.7' (from build '20230303.7' of 'https://github.com/dotnet/installer')
Checking for coherency updates...
Using 'Strict' coherency mode. If this fails, a second attempt utilizing 'Legacy' Coherency mode will be made.
Coherency updates failed for the following dependencies:
Unable to update System.IO.Hashing to have coherency with Microsoft.Dotnet.Sdk.Internal: https://github.com/dotnet/installer @ 9cf0095d0892d385a7e26772752d75e3bb68d8e4 does not contain dependency System.IO.Hashing

In 5d68699, we added a new dependency of System.IO.Hashing from dotnet/runtime.

But for this to work, we'd have to:

1. List System.IO.Hashing as a dependency of dotnet/installer

or

2. Just use manage $(SystemIOHashingPackageVersion) to match the overall version of dotnet/runtime.

In dotnet/maui, at lot of times they've been going with no. 2. If needed on release branches, we can also hardcode the number or switch over to using a stable version on NuGet.org.

Let's remove the Maestro dependency and use $(MicrosoftNETCoreAppRefPackageVersion) for now.

[jonathanpeppers]

The one failure is happening in some other PRs, so I think we can merge:

     (CoreCompile target) -> 
         /Users/runner/work/1/s/xamarin-android/tests/Mono.Android-Tests/Xamarin.Android.Net/AndroidMessageHandlerTests.cs(42,4): error CS0246: The type or namespace name 'RetryAttribute' could not be found (are you missing a using directive or an assembly reference?) [/Users/runner/work/1/s/xamarin-android/tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj]
         /Users/runner/work/1/s/xamarin-android/tests/Mono.Android-Tests/Xamarin.Android.Net/AndroidMessageHandlerTests.cs(42,4): error CS0246: The type or namespace name 'Retry' could not be found (are you missing a using directive or an assembly reference?) [/Users/runner/work/1/s/xamarin-android/tests/Mono.Android-Tests/Runtime-Microsoft.Android.Sdk/Mono.Android.NET-Tests.csproj]

    366 Warning(s)
    2 Error(s)