perf test: Remove x permission from lib/stat_output.sh

The commit fc51fc87 factored out the helper functions to a library
but the new file had execute permission.  Due to the way it detects
the shell test scripts, it showed up in the perf test list unexpectedly.

  $ ./perf test list 2>&1 | grep 86
   76: x86 bp modify
   77: x86 Sample parsing
   78: x86 hybrid
   86:                        <---- (here)

  $ ./perf test -v 86
   86:                                                                 :
  --- start ---
  test child forked, pid 1932207
  test child finished with 0
  ---- end ----
  : Ok

As it's a collection of library functions, it should not run as is.
Let's remove the execute permission.

Fixes: fc51fc87 ("perf test: Move all the check functions of stat CSV output to lib")
Acked-by: Ian Rogers <irogers@google.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230622055832.83476-1-namhyung@kernel.orgSigned-off-by: Namhyung Kim <namhyung@kernel.org>