perf help: Fix a typo ("bellow")

Fix a typo in comments.

Reported-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: kernel-janitors@vger.kernel.org
Link: https://lore.kernel.org/r/20240907131006.18510-1-algonell@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>