perf test: Do not use instructions:u explicitly

perf test: Do not use instructions:u explicitly

I think it's to support non-root user tests.  But perf record can handle
the case and fall back to a software event (cpu-clock).  Practically this
would affect when it's run on a VM, but it seems no reason to prevent running
the test in the guest.

Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221020172643.3458767-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>