After commit 1f265d2aea0dff1f ("selftests/bpf: Remove not used headers"),
tools/arch/s390/include/uapi/asm/ptrace.h has been removed, so remove
it in check-headers.sh too, otherwise we can see the following build
warning:
diff: tools/arch/s390/include/uapi/asm/ptrace.h: No such file or directory