(docs) clear up comments on supporting negative lookbehinds
(docs) clear up comments on supporting negative lookbehinds

carlokok/highlight.js,highlightjs/highlight.js,highlightjs/highlight.js,isagalaev/highlight.js,carlokok/highlight.js,highlightjs/highlight.js,highlightjs/highlight.js,isagalaev/highlight.js,carlokok/highlight.js,carlokok/highlight.js