perf test code-reading: Avoid a leak of cpus and threads

The perf_evlist__set_maps does the necessary gets on the arguments
passed, so the reference count bumping isn't necessary and creates a
memory leak.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250624190326.2038704-3-irogers@google.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>