docs: fix a typo (#1341)

Kouchya · ulivz · commit be88e7f48402 · 2019-02-24T23:57:31.000+08:00
diff --git a/packages/docs/docs/zh/plugin/official/plugin-active-header-links.md b/packages/docs/docs/zh/plugin/official/plugin-active-header-links.md
@@ -32,4 +32,4 @@ module.exports = {
 ### headerAnchorSelector
 
 - 类型: `string`
-- 默认值: `.header-anchor'`
+- 默认值: `.header-anchor`
