Remove explicit SourceLink package and EmbedUntrackedSources for SDK 8+

[dmytroett]

Background

The Source Link README now states that for .NET SDK 8+ projects hosted on GitHub, Source Link support is included by default and no explicit Source Link package reference or build-property opt-in is required.

Reference:

• https://github.com/dotnet/sourcelink/blob/main/README.md#using-source-link-in-net-projects

Current state

src/AttributedDI/AttributedDI.csproj currently has:

• <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="all" />
• <EmbedUntrackedSources>true</EmbedUntrackedSources>

The project targets only SDK-era TFMs:

• net8.0;net9.0;net10.0

Proposal

• Remove Microsoft.SourceLink.GitHub package reference from src/AttributedDI/AttributedDI.csproj.
• Remove explicit <EmbedUntrackedSources>true</EmbedUntrackedSources> from src/AttributedDI/AttributedDI.csproj.
• Keep <PublishRepositoryUrl>true</PublishRepositoryUrl> (still useful for NuGet package metadata).

Why

• Reduces explicit configuration that duplicates SDK defaults.
• Avoids pinning/overriding Source Link package version when SDK already provides it.

Acceptance criteria

• Build/pack still produces symbols and Source Link metadata as expected.
• No regression in package debugging experience for consumers.
• src/AttributedDI/AttributedDI.csproj no longer contains the explicit Source Link package reference or EmbedUntrackedSources property.