performance_test,simplified_invoicing: don't depend on pystone

this is removed from python3, it was not so useful here either

bt5/erp5_performance_test/TestTemplateItem/portal_components/test.erp5.testWorkflowPerformance.py

@@ -25,10 +25,7 @@
 #
 ##############################################################################
 
-from __future__ import print_function
-from test import pystone
 from time import time
-pystone.clock = time
 from erp5.component.test.testPerformance import TestPerformanceMixin
 from Products.ERP5Type.Core.Workflow import ValidationFailed
 from Testing import ZopeTestCase
@@ -72,8 +69,6 @@ class TestWorkflowPerformance(TestPerformanceMixin):
       foo.getSimulationState()
 
     end = time()
-
-    print("\n%s pystones/second" % pystone.pystones()[1])
     message = "\n%s took %.4gs (%s foo(s))" % (self._testMethodName,
                                              end - start, foo_count)
     print(message)

bt5/erp5_simplified_invoicing/TestTemplateItem/portal_components/test.erp5.testSimulationPerformance.py

@@ -28,9 +28,7 @@
 from __future__ import print_function
 import subprocess
 import unittest
-from test import pystone
 from time import time
-pystone.clock = time
 from Products.ERP5Type.tests.runUnitTest import ERP5TypeTestLoader
 from erp5.component.test.testTradeModelLine import TestTradeModelLineSale
 
@@ -58,7 +56,6 @@ class TestSimulationPerformance(TestTradeModelLineSale):
     self.test_01_OrderWithSimpleTaxedAndDiscountedLines()
     self.__class__._order = self['order'].getRelativeUrl()
     self.runAlarms()
-    print("\n%s pystones/second" % pystone.pystones()[1])
 
   def perf_01_invoiceSimpleOrder(self, order_count=1):
     start = time()