update-linux-headers: Remove "asm-s390/unistd_32.h"

The "asm/unistd_32.h" file was generated for the 31-bit compatibility
mode on the s390 architecture and support was removed in v6.19-rc1,
commit 4ac286c4a8d9 ("s390/syscalls: Switch to generic system call
table generation")

unistd_32.h is no longer generated when running make header_install.
Remove it.

Reported-by: Shameer Kolothum <skolothumtho@nvidia.com>
Cc: Thomas Huth <thuth@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260112155341.1209988-1-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

scripts/update-linux-headers.sh

@@ -154,7 +154,6 @@ EOF
     mkdir -p "$output/include/standard-headers/asm-$arch"
     if [ $arch = s390 ]; then
         cp_portable "$hdrdir/include/asm/virtio-ccw.h" "$output/include/standard-headers/asm-s390/"
-        cp "$hdrdir/include/asm/unistd_32.h" "$output/linux-headers/asm-s390/"
         cp "$hdrdir/include/asm/unistd_64.h" "$output/linux-headers/asm-s390/"
     fi
     if [ $arch = arm64 ]; then