Revert "Make code more complain with node 6"

This reverts commit a35339f.

Author: armano2

lib/rules/use-v-on-exact.js

@@ -43,8 +43,11 @@ module.exports = {
               return rv
             }, {})
 
-          for (const group of groups) {
-            if (group.length > 1 && group.some(item => item.modifiers.length > 0)) { // check if there are directives with modifiers
+          const directives = Object.keys(groups).map(key => groups[key])
+          // const directives = Object.values(groups) // Uncomment after node 6 is dropped
+            .filter(item => item.length > 1)
+          for (const group of directives) {
+            if (group.some(item => item.modifiers.length > 0)) { // check if there are directives with modifiers
               const invalid = group.filter(item => item.modifiers.length === 0)
               for (const node of invalid) {
                 context.report({