remove old workaround for shortcuts now causing issues

Old issue seems to be fixed in Qt 5.15 LTS and Qt 6.
Old workaround causes error "QAction::event: Ambiguous shortcut overload" now in latest Qt versions, at least when creating shortcuts for actions like "tool selection".

Author: e-d-n-a

pyzo/core/menu.py

@@ -236,9 +236,6 @@ def setShortcut(self, action):
             # Set shortcut so Qt can do its magic
             shortcuts = pyzo.config.shortcuts2[action.menuPath]
             action.setShortcuts(shortcuts.split(","))
-            pyzo.main.addAction(
-                action
-            )  # issue #470, http://stackoverflow.com/questions/23916623
             # Also store shortcut text (used in display of tooltip
             shortcuts = shortcuts.replace(",", ", ").replace("  ", " ")
             action._shortcutsText = shortcuts.rstrip(", ")