testKM: Remove knowledge_pad.visible after creation

After some debugs in this file and Products/DCWorkflow/DCWorkflow.py.
I found after creation, the Knowledge state is already 'visible'
Maybe related to https://lab.nexedi.com/vpelletier/erp5/commit/59e7ed2946b612076ad21623f80c4e2f50f64199#diff-3
But not 100% sure. Wait Vincent confirm it.

product/ERP5/tests/testKM.py

@@ -133,8 +133,6 @@ class TestKM(TestKMMixIn):
                                                        mode = 'web_section')
     self.web_section_content_knowledge_pad = portal.restrictedTraverse(
                                           self.web_section_content_knowledge_pad_relative_url)
-    self.web_front_knowledge_pad.visible()
-    self.web_section_knowledge_pad.visible()
     self.tic()
     # Publish all knowledge pad gadgets
     for gadget in self.portal.portal_gadgets.objectValues():