mm/swapfile: remove duplicate include of swap_table.h

mm/swapfile: remove duplicate include of swap_table.h

Remove duplicate inclusion of swap_table.h in swapfile.c to clean up
redundant code.

Link: https://lkml.kernel.org/r/20260318043849.399266-1-nichen@iscas.ac.cn
Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>