[skip ci]Fix default log dir name for script (#11378)

Signed-off-by: zhuwenxing <wenxing.zhu@zilliz.com>

tests/scripts/export_log_k8s.sh

@@ -3,7 +3,7 @@ set -e
 
 ns_name=$1
 prefix_name=$2
-log_dir=${3:-"k8s_log"}
+log_dir=${3:-"k8s_logs"}
 array=($(kubectl get pod -n ${ns_name}|grep ${prefix_name}|awk '{print $1}'))
 echo ${array[@]}
 if [ ! -d $log_dir  ];