Update src/nuget.config

Co-authored-by: Steve Sanderson <[email protected]>

Author: mkArtakMSFT

src/nuget.config

@@ -4,6 +4,5 @@
         <!--To inherit the global NuGet package sources remove the <clear/> line below -->
         <clear />
         <add key="nuget" value="https://api.nuget.org/v3/index.json" />
-        <add key="dotnet5" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5/nuget/v3/index.json" />
     </packageSources>
-</configuration>
+</configuration>