selftests/bpf: Remove test_task_storage_map_stress_lookup

Remove a test in test_maps that checks if the updating of the percpu
counter in task local storage map is preemption safe as the percpu
counter is now removed.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260205222916.1788211-16-ameryhung@gmail.com

Author: ameryhung