perf script: Fix outdated comment for perf-trace-python

perf script: Fix outdated comment for perf-trace-python

Script generated by the '--gen-script' option contains an outdated
comment. It mentions a 'perf-trace-python' document while it has been
renamed to 'perf-script-python'. Fix it.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 9661ee08482a ("perf: Rename 'perf trace' to 'perf script'")
Link: http://lkml.kernel.org/r/20170530111827.21732-2-sj38.park@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>