perf tests stat+json_output: Address shellcheck warnings

Running shellcheck on stat+json_output testcase, generates below warning:

	 [ $(id -u) != 0 ] && [ $(cat /proc/sys/kernel/perf_event_paranoid) -gt $1 ]
           ^------^ SC2046 (warning): Quote this to prevent word splitting.
                                ^-- SC2046 (warning): Quote this to prevent word splitting.

Fixed the warning by adding quotes to avoid word splitting.

ShellCheck result with patch:
	 # shellcheck -S warning stat+json_output.sh
	 #

perf test result after the change:
	 94: perf stat JSON output linter : Ok

Signed-off-by: Disha Goel <disgoel@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/linux-perf-users/20230613164145.50488-3-atrajeev@linux.vnet.ibm.com


Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>