Improve warning wording in vue/no-v-for-template-key-on-child docs (vuejs#1859)

Co-authored-by: Flo Edelmann <[email protected]>

Author: yammyxing

docs/rules/no-v-for-template-key-on-child.md

@@ -20,8 +20,8 @@ In Vue.js 3.x, with the support for fragments, the `<template v-for>` key can be
 See [Migration Guide - `key` attribute > With `<template v-for>`](https://v3-migration.vuejs.org/breaking-changes/key-attribute.html#with-template-v-for) for more details.
 
 ::: warning Note
-Do not use with the [vue/no-v-for-template-key] rule for Vue.js 2.x.  
-This rule conflicts with the [vue/no-v-for-template-key] rule.
+This rule is targeted at Vue.js 3.x.
+If you are using Vue.js 2.x, enable the [vue/no-v-for-template-key] rule instead. Don't enable both rules together; they are conflicting.
 :::
 
 <eslint-code-block :rules="{'vue/no-v-for-template-key-on-child': ['error']}">