hide popover when doc is edited or changes
merge with master
use getActiverEditor()
activeEditorChange gets called same time as currentDocumentChange, so no need to listen to both
no need to keep track of doc we're listening to
Ensure disabling Hover Preview detaches its listener from whatever document
it was last attached to.
Merge pull request #3538 from adobe/randy/hover-preview-dismiss

Hide Hover Preview popover when doc is edited or switched