C#: Remove isNullOrEmpty check as it is implied by the case above.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/FeedManager.cs

@@ -141,10 +141,7 @@ private IEnumerable<string> GetFeeds(Func<IList<string>> getNugetFeeds)
                     continue;
                 }
 
-                if (!string.IsNullOrWhiteSpace(url))
-                {
-                    yield return url;
-                }
+                yield return url;
             }
         }