improve grep pattern for ipv6 sets

metrics.sh

@@ -111,9 +111,9 @@ function printMetrics() {
   for v in "" 6; do
     ipset list -t | grep -e "^N" | xargs -L 2 | awk '/^Name: tor-/ { print $2, $6 }' |
       if [[ $v == "6" ]]; then
-        grep -e "[a-z]6 " -e "[a-z]6-"
+        grep -E -e "-[a-z]+6[ -]"
       else
-        grep -v -e "[a-z]6 " -e "[a-z]6-"
+        grep -v -E -e "-[a-z]+6[ -]"
       fi |
       while read -r name size; do
         mode=$(cut -f 2 -d '-' -s <<<$name | tr -d '6')