Fix link to CI nuget feed

Author: AArnott

CONTRIBUTING.md

@@ -72,7 +72,7 @@ via `[Fact(Skip = "Test does not pass yet")]` or similar message to keep our tes
 As soon as you send a pull request, a build is executed and updated NuGet packages
 are published to this Package Feed:
 
-    https://ci.appveyor.com/nuget/Nerdbank.GitVersioning
+    https://ci.appveyor.com/nuget/nerdbank-gitversioning
 
 By adding this URL to your package sources you can immediately install your version
 of the NuGet packages to your project. This can be done by adding a nuget.config file
@@ -82,7 +82,7 @@ with the following content to the root of your project's repo:
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
     <packageSources>
-        <add key="Nerdbank.GitVersioning CI" value="https://ci.appveyor.com/nuget/Nerdbank.GitVersioning" />
+        <add key="Nerdbank.GitVersioning CI" value="https://ci.appveyor.com/nuget/nerdbank-gitversioning" />
     </packageSources>
 </configuration>
 ```