Fix HTML hinting issues caused by new token types -- "error" and "tag error".

"error" was introduced in https://github.com/marijnh/CodeMirror/commit/32abe85e698644231dba3badac86e886312461fd and then caused #5343. "tag error" was introduced in https://github.com/marijnh/CodeMirror/commit/a6c2e01fce24c960c7bf58118fce337fd054a6db and will break tag hinting when we update CodeMirror for sprint-33. Tag hints won't show up when you type a `<`. So this needs to land in master before landing the next CodeMirror update.