selftests/bpf: Remove exceptions tests from DENYLIST.s390x

Now that the s390x JIT supports exceptions, remove the respective tests
from the denylist.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240703005047.40915-4-iii@linux.ibm.com