Updated FilterAliasAttribute to use nameof(alias) when throwing an ArgumentNullException when the alias param is null or empty. (#146)

Author: brental

src/Microsoft.FeatureManagement/FilterAliasAttribute.cs

@@ -18,7 +18,7 @@ public FilterAliasAttribute(string alias)
         {
             if (string.IsNullOrEmpty(alias))
             {
-                throw new ArgumentNullException(alias);
+                throw new ArgumentNullException(nameof(alias));
             }
 
             Alias = alias;