[GH Usage] Updated GH Usage Config class documentation

Author: mogah

src/NuGetGallery.Core/GitHub/IGitHubUsageConfiguration.cs

@@ -4,11 +4,11 @@ public interface IGitHubUsageConfiguration
     {
         /// <summary>
         /// Returns a NuGetPackageGitHubInformation object that contains the information about a NuGet package.
-        /// NOTE: If a packageId has no information, the NuGetPackageGitHubInformation's TotalRepos will be 0
+        /// If a packageId has no information, the NuGetPackageGitHubInformation's TotalRepos will be 0
         /// and the Repos list will be empty
         /// 
-        /// throws an ArgumentException if the packageId is null
         /// </summary>
+        /// <exception cref="System.ArgumentNullException">Thrown when packageId is null</exception>
         /// <param name="packageId">NuGet package id, cannot be null</param>
         /// <returns></returns>
         NuGetPackageGitHubInformation GetPackageInformation(string packageId);