Increase input thread polling frequency

This does not have a significant impact on cpu usage in my testing (~+0.5% cpu on a 4-core system) and should improve input latency by 4ms on average.

src/BizHawk.Client.EmuHawk/Input/Input.cs

@@ -266,7 +266,7 @@ namespace BizHawk.Client.EmuHawk
 				} //lock(this)
 
 				//arbitrary selection of polling frequency:
-				Thread.Sleep(10);
+				Thread.Sleep(2);
 			}
 		}