Bump Microsoft.SourceLink.GitHub from 1.1.1 to 8.0.0

Bumps [Microsoft.SourceLink.GitHub](https://github.com/dotnet/sourcelink) from 1.1.1 to 8.0.0.
- [Release notes](https://github.com/dotnet/sourcelink/releases)
- [Commits](dotnet/sourcelink@1.1.1...8.0.0)

---
updated-dependencies:
- dependency-name: Microsoft.SourceLink.GitHub
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

src/RxFree/RxFree.csproj

@@ -29,7 +29,7 @@ System.Reactive package for `IObservable<T>` producers.
 
   <ItemGroup>
     <PackageReference Include="NuGetizer" Version="1.0.5" />
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="all" />
   </ItemGroup>
 
 </Project>