spacemanager: Drop 'fix missing size' command

The command was used to recover from a bug in dCache 1.9.1 and
is no longer needed.

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Acked-by: Dmitry Litinvtsev <litvinse@fnal.gov>
Patch: http://rb.dcache.org/r/6372/