Simplify implementation of fiber_wake_on_event()

Align fork-on-block implementation of fiber_wake_on_event() with that of fiber_sleep() and MicroBitLock::wait().

This patch has no impact on external behaviour, but introduces a consistent
deisgn pattern for fork-on-block handling within the scheduler.

Author: finneyj

source/core/MicroBitFiber.cpp

@@ -428,12 +428,7 @@ int fiber_wake_on_event(uint16_t id, uint16_t value)
         // If we're out of memory, there's nothing we can do.
         // keep running in the context of the current thread as a best effort.
         if (forkedFiber != NULL)
-        {
             f = forkedFiber;
-            dequeue_fiber(f);
-            queue_fiber(f, &runQueue);
-            schedule();
-        }
     }
 
     // Encode the event data in the context field. It's handy having a 32 bit core. :-)