message: docs(theme): fix migration guide
diff: @@ -186,7 +186,9 @@ Since the theme no longer has a built-in search:
  Move all plugin related options under `plugins`.
  -- move `activeHeaderLinks` to `plugins.activeHeaderLinks`
  +- rename `activeHash` to `plugins.activeHeaderLinks`
  +
  + The theme now uses official plugin `@vuepress/plugin-active-header-links`.
  - move `comment` moved to `plugins.comment`
  @@ -244,10 +246,6 @@ Move all plugin related options under `plugins`.
  ### Deletion
  -- remove `activeHash`
  -
  - The theme now uses official plugin `@vuepress/plugin-active-header-links`.
  -
  - remove `addThis`
  `vuepress-plugin-add-this` V2 was marked as deprecated when migrating and the theme no longer bundles it by default.
  