Updates the RID graph to include Android 30 - #45442

Fixes: dotnet/sdk#14908

In a .NET 6 Android project, adding a NuGet package such as:

    <PackageReference Include="akavache" Version="6.0.30"/>

...would include Linux native libraries from dependencies, such as:

    packages\sqlitepclraw.lib.e_sqlite3.linux\1.1.11\runtimes\linux-arm64\native\libe_sqlite3.so

Comparing the RID graph for iOS and Android in
`dotnet\sdk\*\RuntimeIdentifierGraph.json`:

    "ios": {
      "#import": [
        "unix"
      ]
    },
    ...
    "android": {
      "#import": [
        "linux"
      ]
    },

It seems like Android graph should match iOS here, as changing `linux`
-> `unix` solved this issue for me locally.

Based on the changes in dotnet#45442, I updated `runtimeGroups.props` to
specify `linux` instead of `unix` for Android. Then I ran this command
to update the checked-in `.json` files:

    > dotnet build .\src\libraries\pkg\Microsoft.NETCore.Platforms -p:UpdateRuntimeFiles=true