fix small nits

src/csharp/Grpc.Microbenchmarks/CommonThreadedBase.cs

@@ -35,7 +35,7 @@ namespace Grpc.Microbenchmarks
     {
         protected virtual bool NeedsEnvironment => true;
 
-        [Params(1, 1, 2, 4, 8, 12)]
+        [Params(1, 2, 4, 8, 12)]
         public int ThreadCount { get; set; }
 
         protected GrpcEnvironment Environment { get; private set; }

src/csharp/Grpc.Microbenchmarks/CompletionRegistryBenchmark.cs

@@ -22,7 +22,7 @@ using Grpc.Core.Internal;
 
 namespace Grpc.Microbenchmarks
 {
-    public class CompletionRegistryBenchmarks : CommonThreadedBase
+    public class CompletionRegistryBenchmark : CommonThreadedBase
     {
         [Params(false, true)]
         public bool UseSharedRegistry { get; set; }