getAnonymousNodes() and getBindingParent() removed from fx72

getAnonymousNodes() and getBindingParent() removed from fx72

see also: https://bugzil.la/1596800

the whole XULDocument code path in
markable-elements.coffee::getAllElements() is now obsolete, since
getAnonymousNodes() no longer exists, and before that, returned nothing
of importance, since most XBL bindings have been removed before Firefox
68. Removal of the code path will follow in a follow up to ease a
possible revert, since a very small amount of hints might get lost in
68esr without it (the only concrete example I've found is the urlbar in
'eb' mode, which can also be reached with 'o').