Remove any bindings attached to key in given contexts. contexts is a list of event-contexts (e.g., '(left-button-1 frame-sides)) key is a string giving the key-specifier (e.g., M-Delete for Meta+Delete). The return value is #t if the binding was removed successfully, #f otherwise. ignored-proc1 and ignored-proc2 can both be given, but are ignored; they permit the identical arguments to be used as for bind-mouse.