selftest/bpf/benchs: Fix a typo in bpf_hashmap_full_update

To call the bpf_hashmap_full_update benchmark, one should say:

    bench bpf-hashmap-ful-update

The patch adds a missing 'l' to the benchmark name.

Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230213091519.1202813-2-aspsk@isovalent.com