some pointless HeapTupleHeaderIndicatesMovedPartitions calls

Hello

Pavan Deolasee recently noted that a few of the
HeapTupleHeaderIndicatesMovedPartitions calls added by commit
5db6df0c0117 are useless, since they are done after comparing t_self
with t_ctid.  That's because t_self can never be set to the magical
values that indicate that the tuple moved partition.  If the first
test fails (so we know t_self equals t_ctid), necessarily the second
test will also fail.

So these checks can be removed and no harm is done.

-- 
Álvaro Herrera                            39°49'30"S 73°17'W