fix incorrect links in the classic/documentation/restful-queue

[levrun]

The links in the https://activemq.apache.org/components/classic/documentation/restful-queue lead nowhere:

• the discussion on rest-discuss
• httplr

This site can’t be reachedtech.groups.yahoo.com’s server IP address could not be found.

We couldn't find the page you were looking for. 

I updated the links so that readers can get the info about httplr and discussion on rest faster.