perf tests: Fix shellcheck warning in stat_all_metricgroups

Running shellcheck on stat_all_metricgroups.sh reports
below warning:

 In ./tests/shell/stat_all_metricgroups.sh line 7:
 function ParanoidAndNotRoot()
 ^-- SC2112: 'function' keyword is non-standard. Delete it.

As per the format, "function" is a non-standard keyword that
can be used to declare functions. Fix this by removing the
"function" keyword from ParanoidAndNotRoot function
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: kjain@linux.ibm.com
Cc: maddy@linux.ibm.com
Cc: disgoel@linux.vnet.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20231013073021.99794-4-atrajeev@linux.vnet.ibm.comSigned-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/tests/shell/stat_all_metricgroups.sh

@@ -4,7 +4,7 @@
 
 set -e
 
-function ParanoidAndNotRoot()
+ParanoidAndNotRoot()
 {
   [ "$(id -u)" != 0 ] && [ "$(cat /proc/sys/kernel/perf_event_paranoid)" -gt $1 ]
 }