Removed external packages feeds (#1524)

Co-authored-by: Tracy Boehrer <trboehre@microsoft.com>

tests/unit/packages/Microsoft.Bot.Components.Telephony.Tests/NuGet.Config

@@ -3,6 +3,5 @@
   <packageSources>
     <clear />
     <add key="SDK" value="https://pkgs.dev.azure.com/ConversationalAI/BotFramework/_packaging/SDK/nuget/v3/index.json" />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
 </configuration>

tests/unit/skills/calendar/NuGet.Config

@@ -3,6 +3,5 @@
   <packageSources>
     <clear />
     <add key="SDK" value="https://pkgs.dev.azure.com/ConversationalAI/BotFramework/_packaging/SDK/nuget/v3/index.json" />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
 </configuration>

tests/unit/skills/common/NuGet.Config

@@ -3,6 +3,5 @@
   <packageSources>
     <clear />
     <add key="SDK" value="https://pkgs.dev.azure.com/ConversationalAI/BotFramework/_packaging/SDK/nuget/v3/index.json" />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
 </configuration>