chore: remove unused SourceLink package versions

The central package list no longer includes the Azure Repos and GitHub
SourceLink version pins.

Author: matt-edmondson

Directory.Packages.props

@@ -4,8 +4,6 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="CommandLineParser" Version="2.9.1" />
-    <PackageVersion Include="Microsoft.SourceLink.AzureRepos.Git" Version="10.0.300" />
-    <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="10.0.300" />
     <PackageVersion Include="Polyfill" Version="9.3.0" />
     <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.12" />
     <PackageVersion Include="ktsu.Extensions" Version="1.5.9" />