osd: drop broken (and useless) PG::merge_log assert
osd: drop broken (and useless) PG::merge_log assert

The assert should be olog.backlog, not log.backlog.  But it's the same
condition as the if guard that's 3 lines up, making it pretty useless.
Just drop it.

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph