mon: remove utime_t param in _dump

mon: remove utime_t param in _dump

Missing in af720cc87b4d631695c1549c31d57bfbc82bc6ba.

Found in warning:

In file included from /home/pdonnell/ceph/src/mds/MDSRank.h:18:0,
                 from /home/pdonnell/ceph/src/mds/MDBalancer.cc:18:
/home/pdonnell/ceph/src/common/TrackedOp.h:153:16: warning: ‘virtual void TrackedOp::_dump(ceph::Formatter*) const’ was hidden [-Woverloaded-virtual]
   virtual void _dump(Formatter *f) const {}
                ^
In file included from /home/pdonnell/ceph/src/mon/mon_types.h:23:0,
                 from /home/pdonnell/ceph/src/mon/MonMap.h:22,
                 from /home/pdonnell/ceph/src/mon/MonClient.h:20,
                 from /home/pdonnell/ceph/src/mds/MDBalancer.cc:19:
/home/pdonnell/ceph/src/mon/MonOpRequest.h:106:8: warning:   by ‘void MonOpRequest::_dump(utime_t, ceph::Formatter*) const’ [-Woverloaded-virtual]
   void _dump(utime_t now, Formatter *f) const {
        ^

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>