message: fix: make transition-group key warning a tip to avoid breaking compilation
diff: @@ -341,7 +341,8 @@ function processKey (el) {
  if (iterator && iterator === exp && parent && parent.tag === 'transition-group') {
  warn(
  `Do not use v-for index as key on <transition-group> children, ` +
  - `this is the same as not using keys.`
  + `this is the same as not using keys.`,
  + true /* tip */
  )
  }
  }
  