Update Microsoft.SourceLink.GitHub package.

Author: bgrainger

src/Directory.Build.props

@@ -22,7 +22,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19367-01" PrivateAssets="All"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19554-01" PrivateAssets="All"/>
   </ItemGroup>
 
   <ItemGroup>