Update action button when updating the list of card keys

When the certificate belonging to a card key is imported from the card
or deleted locally then we need to update the action button of the
corresponding list item. We only need to do this if there's only one
action (because the menu actions are updated whenever the menu is opened).

(cherry picked from commit f70aa609806756d8805e359389de8b2f3ac3966a)

• GnuPG-bug-id: T7413