Update NuGet package sources

Author: mattbrailsford

NuGet.config

@@ -5,18 +5,4 @@
     <add key="Umbraco Prereleases" value="https://www.myget.org/F/umbracoprereleases/api/v3/index.json" />
     <add key="Umbraco Nightly" value="https://www.myget.org/F/umbraconightly/api/v3/index.json" />
   </packageSources>
-  <packageSourceMapping>
-    <packageSource key="nuget.org">
-      <package pattern="Umbraco.*" />
-      <package pattern="*" />
-    </packageSource>
-    <packageSource key="Umbraco Prereleases">
-      <package pattern="Umbraco.Licenses" />
-      <package pattern="Umbraco.Commerce.*" />
-    </packageSource>
-    <packageSource key="Umbraco Nightly">
-      <package pattern="Umbraco.Licenses" />
-      <package pattern="Umbraco.Commerce.*" />
-    </packageSource>
-  </packageSourceMapping>
 </configuration>