Remove "title_of_topic" part from URL

Seeing as they don't really serve a purpose (that I know of) other than letting people know the title of the topic before they click. Do we need to keep them around?

Original link:

https://tildes.net/~tildes.official/83l/topics_and_comments_can_now_be_bookmarked_aka_saved

Works just fine without it:

https://tildes.net/~tildes.official/83l

And changing the "title_of_topic"-part in the URL has no effect:

https://tildes.net/~tildes.official/83l/this_is_not_the_topic_title_but_it_still_works