docs: fix example in halmodule

Author: hansu

docs/src/hal/halmodule.txt

@@ -317,9 +317,9 @@ And have a function to be called:
 [source,python]
 ----
     def _on_example_trigger_change(self,pin,userdata=None):
-        print "pin value changed to:" % (pin.get())
-        print "pin name= %s" % (pin.get_name())
-        print "pin type= %d" % (pin.get_type())
+        print "pin value changed to: {}".format(pin.get())
+        print "pin name= {}".format(pin.get_name())
+        print "pin type= {}".format(pin.get_type())
 
         # this can be called outside the function
         self.example_trigger.get()