shell: remove 'annotate-selected-text' action

which was used in the EvView context menu, and use instead highlight-text action, which provides the same functionality (highlighting selected text) but with the added bonus of showing the keybinding (Ctrl+H) in the context menu.

In case the action was disabled for the context menu we need to enable it back again when closing the menu and returning to normal view, we do that in the menu "hide" signal handler.

Closes #1919 (closed)