kernel: pid_namespace: remove unused set_memfd_noexec_scope()

This inline function is unused, remove it.

Link: https://lkml.kernel.org/r/20230610102858.31488-1-yuehaibing@huawei.com


Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>