Delete NuGet.config (#16)

- file prevents use of `darc` feeds in dotnet/aspnetcore
- cannot be automatically kept in sync w/ the file in dotnet/aspnetcore

NuGet.config

@@ -1,16 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <packageSources>
-    <clear />
-    <add key="dotnet-eng" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json" />
-    <add key="dotnet7" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet7/nuget/v3/index.json" />
-    <!-- Required when building within dotnet/aspnetcore. -->
-    <add key="dotnet7-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet7-transport/nuget/v3/index.json" />
-    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
-    <!-- Required when building within dotnet/aspnetcore. -->
-    <add key="dotnet6-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6-transport/nuget/v3/index.json" />
-  </packageSources>
-  <disabledPackageSources>
-    <clear />
-  </disabledPackageSources>
-</configuration>