Removed unused constant

src/main/java/com/loomcom/symon/Cpu.java

@@ -55,10 +55,6 @@ public class Cpu implements InstructionTable {
     public static final int IRQ_VECTOR_L = 0xfffe;
     public static final int IRQ_VECTOR_H = 0xffff;
 
-    // The delay in microseconds between steps.
-    // TODO: Make configurable
-    private static final int CLOCK_IN_NS = 1000;
-
     /* Simulated behavior */
     private static CpuBehavior behavior;