Improve code quality

Author: theSlyest

Parse/Platform/LiveQueries/ParseLiveQuery.cs

@@ -60,10 +60,7 @@ public ParseLiveQuery(IServiceHub serviceHub, string className, IDictionary<stri
     /// </summary>
     private ParseLiveQuery(ParseLiveQuery<T> source, IEnumerable<string> watchedKeys = null)
     {
-        if (source == null)
-        {
-            throw new ArgumentNullException(nameof(source));
-        }
+        ArgumentNullException.ThrowIfNull(source);
 
         Services = source.Services;
         ClassName = source.ClassName;