Remove help icon which advertises keyboard shortcuts

It was reported in a User Guide issue that the keyboard shortcuts documented for the UI don't actually work. Coleman suggested on Mattermost that instead of trying to fix them, we resign ourselves to the fact that they don't work and remove the documentation about it. We already have User Guide #168 to track the needed changes to the User Guide. This ticket is to track the needed changes to CiviCRM.

I suggest the following modification to CiviCRM core: remove the help icon "Access Keys" which appears at the bottom right of just about every screen.