Make seahorse tests more robust by using less keyboard shortcuts
_Originally created by @anonym on [#9343 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/9343)_
Series of keyboard shortcuts are known to not work well, since Sikuli
issues them so fast that later ones may get lost.
Feature Branch: kytv:test/9343-access-seahorse-menus-with-the-mouse
Parent Task: tails/tails#9095
issue