Fix scheduler warning

```
test/fiber/test_scheduler.rb:98: warning: Scheduler should implement #fiber_interrupt
```

Author: byroot

test/fiber/test_scheduler.rb

@@ -94,6 +94,9 @@ def scheduler.io_wait
     def scheduler.kernel_sleep
     end
 
+    def scheduler.fiber_interrupt(_fiber, _exception)
+    end
+
     thread = Thread.new do
       Fiber.set_scheduler scheduler
     end