Removed redundant check

Author: alinasmirnova

src/BenchmarkDotNet/Code/CodeGenerator.cs

@@ -93,7 +93,7 @@ internal static string Generate(BuildPartition buildPartition)
 
         private static void AddNonEmptyUnique(HashSet<string> items, string value)
         {
-            if (!string.IsNullOrEmpty(value) && !items.Contains(value))
+            if (!string.IsNullOrEmpty(value))
                 items.Add(value);
         }