Revert "update vuepress to v2.0.0-rc.19"

This reverts commit 8772da1.

Author: xiaokangwang

package.json

@@ -14,7 +14,7 @@
     "@vuepress/plugin-docsearch": "^2.0.0-beta.61",
     "@vuepress/plugin-register-components": "^2.0.0-beta.61",
     "lint-staged": "^15.4.3",
-    "vuepress": "^v2.0.0-rc.19"
+    "vuepress": "^2.0.0-beta.61"
   },
   "dependencies": {
     "uuid": "^11.0.5"