xt_MASQUERADE.ko is picked up by both kmod-ipt-nat and kmod-ipt-nat6, causing
conflict
As kmod-ipt-nat6 already depends on kmod-ipt-nat, remove xt_MASQUERADE from it
Fixes: FS#2924
Fixes: 0fad8af85158 ("kernel: Include xt_MASQUERADE for kernel 5.2 and later")
Signed-off-by: DENG Qingfang <dengqf6@mail2.sysu.edu.cn>