call pywikibot.showHelp() instead of raising NoEnoughData

in add_text.py and commonscat.py

- the expected failures were removed from script_tests.py

- the 'addText' argument of add_text.add_text()
  is now mandatory

bug: 69091
Change-Id: I23f8a29ad5864be6ff649ad7a2c59e0810d9c7c3
Merge "call pywikibot.showHelp() instead of raising NoEnoughData"