katebookmarks: always populate the menu with some actions

Otherwise this menu entry is not shown on macOS until bookmarkMenuAboutToShow is called by e.g. opening the context menu in a document and hovering over the "Bookmarks" entry, or macOS' menu searching feature.

before this change the menu would appear out of nowhere :)
Screen_Recording_2022-02-25_at_21.01.01

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