test: Shorten object core API stats test name

Changing the name of the routine test_obj_core_stats_deregister()
to something shorter (test_obj_core_stats_dereg) has been found to
be a workaround to the issue identified in #61087.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>

tests/kernel/obj_core/obj_core_stats_api/src/main.c

@@ -216,7 +216,7 @@ ZTEST(obj_core_stats_api, test_obj_core_stats_raw)
 	k_mutex_unlock(&test_mutex);
 }
 
-ZTEST(obj_core_stats_api, test_obj_core_stats_deregister)
+ZTEST(obj_core_stats_api, test_obj_core_stats_dereg)
 {
 	int  status;
 	char buffer[sizeof(struct k_cycle_stats)];