perf/x86/intel/bts: Fix comment about default perf_event_paranoid setting

The default paranoid setting was updated in commit 0161028b
("perf/core: Change the default paranoia level to 2") so this comment is
no longer true.

Signed-off-by: James Clark <james.clark@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240802105256.335961-1-james.clark@linaro.org