Remove redundant empty statements.

Rx.NET/Source/src/System.Reactive/Internal/ScheduledObserver.cs

@@ -446,7 +446,6 @@ namespace System.Reactive
         {
             while (q.TryDequeue(out var _))
             {
-                ;
             }
         }
 

Rx.NET/Source/src/System.Reactive/Internal/SystemClock.Default.cs

@@ -106,7 +106,7 @@ namespace System.Reactive.PlatformServices
                 {
                     Task.Delay((int)SyncMaxDelta).Wait();
                 }
-            };
+            }
         }
 
         private void TimeChanged()

Rx.NET/Source/src/System.Reactive/Linq/Observable/ConcatMany.cs

@@ -129,7 +129,6 @@ namespace System.Reactive.Linq.ObservableImpl
                     {
                         while (_queue.TryDequeue(out var _))
                         {
-                            ;
                         }
                     }
                     else