perf python: Fix spelling mistake "metics" -> "metrics"

perf python: Fix spelling mistake "metics" -> "metrics"

There is a spelling mistake in a Python doc string. Fix it.

Fixes: d0550be70f7ab84d ("perf python: Add parse_metrics function")
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: kernel-janitors@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250904090904.2782814-1-colin.i.king@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>