mq: fix the deprecation comment for qsave & qrestore. Changeset bcf90e712dc3 deprecated qsave and qrestore. In the deprecating comment, users were referred to 'rebase --mq' which -- at the time the message was written -- didn't exist. Currently, on the default branch, rebase *does* take a '--mq' option, but it probably doesn't do what Dirkjan expected it to do when he wrote the message. In the original, deprecating commit, little context was provided as to why this change was made. Based on my recollection, concensus at the Paris Sprint in February 2010 was that one of the problems with MQ was that it exposed far too many commands. Notable among these were qsave & qrestore: very few core developers understood what they did and even fewer (none, IIRC) actually used them. However, they couldn't be removed; not only do the usual backwards compatibility reasons apply, but the hg book refers to them.