8358448: JFR: Incorrect time unit for MethodTiming event

Reviewed-by: mgronlun, ayang

Author: egahlin

src/jdk.jfr/share/classes/jdk/jfr/events/MethodTimingEvent.java

@@ -43,7 +43,7 @@ public final class MethodTimingEvent extends AbstractJDKEvent {
     public long invocations;
 
     @Label("Average Time")
-    @Timespan
+    @Timespan(Timespan.TICKS)
     public long average;
 
     public static void commit(long start, long method, long invocations, long average) {