selftests/bpf: drop test_bpftool.sh

selftests/bpf: drop test_bpftool.sh

The test_bpftool.sh script runs a python unittest script checking
bpftool json output on different commands. As part of the ongoing effort
to get rid of any standalone test, this script should either be
converted to test_progs or removed.

As validating bpftool json output does not bring much value to the test
base (and because it would need test_progs to bring in a json parser),
remove the standalone test script.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/20260227-bpftool_feature-v1-1-a25860fd52fb@bootlin.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>