mm/mm_init.c: remove the outdated code comment above deferred_grow_zone()

mm/mm_init.c: remove the outdated code comment above deferred_grow_zone()

The noinline attribute has been taken off in commit 9420f89db2dd ("mm:
move most of core MM initialization to mm/mm_init.c").  So remove the
unneeded code comment above deferred_grow_zone().

And also remove the unneeded bracket in deferred_init_pages().

Link: https://lkml.kernel.org/r/20240326061134.1055295-6-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>