message: fix(theme): fix deprecate msg
diff: @@ -7,7 +7,7 @@ import { colors } from "@vuepress/utils";
  const DEPRECATED_FRONTMATTER_OPTIONS: [string, string][] = [
  ["authors", "author"],
  ["categories", "category"],
  - ["tags", "tags"],
  + ["tags", "tag"],
  ["time", "date"],
  ["visitor", "pageview"],
  ["sidebarDepth", "headerDepth"],
  