Reverting 2 locks based on review feedback and early measurements

src/Servers/Kestrel/Core/src/Internal/Http2/FlowControl/InputFlowControl.cs

@@ -25,7 +25,7 @@ internal sealed class InputFlowControl
     private FlowControl _flow;
     private int _pendingUpdateSize;
     private bool _windowUpdatesDisabled;
-    private readonly Lock _flowLock = new();
+    private readonly object _flowLock = new();
 
     public InputFlowControl(uint initialWindowSize, uint minWindowSizeIncrement)
     {

src/Servers/Kestrel/Core/src/Internal/Http2/Http2FrameWriter.cs

@@ -99,7 +99,7 @@ internal sealed class Http2FrameWriter
     private bool _completed;
     private bool _aborted;
 
-    private readonly Lock _windowUpdateLock = new();
+    private readonly object _windowUpdateLock = new();
     private long _connectionWindow;
     private readonly Queue<Http2OutputProducer> _waitingForMoreConnectionWindow = new();
     // This is the stream that consumed the last set of connection window