Revert chrono update to period and delay for userallocated events

Userallocated events have not been converted to use chrono types
and thus the associated snippet needs those changes reverted until
such time as UserAllocatedEvent is updated.

Author: adbridge

APIs_RTOS/UserAllocatedEvent_ex_1/main.cpp

@@ -71,17 +71,17 @@ int main()
     Thread event_thread;
 
     // The event can be manually configured for special timing requirements.
-    // Timings are specified in milliseconds expressed as Chrono durations
+    // Timings are specified in milliseconds.
     // Starting delay - 100 msec
     // Delay between each event - 200msec
-    event1.delay(100ms);
-    event1.period(200ms);
-    event2.delay(100ms);
-    event2.period(200ms);
-    event3.delay(100ms);
-    event3.period(200ms);
-    event4.delay(100ms);
-    event4.period(200ms);
+    event1.delay(100);
+    event1.period(200);
+    event2.delay(100);
+    event2.period(200);
+    event3.delay(100);
+    event3.period(200);
+    event4.delay(100);
+    event4.period(200);
 
     event_thread.start(callback(post_events));