chore(deps): roll back dependency @babel/plugin-external-helpers to 7.0.0-beta.52 (#123)

Author: renovate[bot]

package.json

@@ -36,7 +36,7 @@
   "devDependencies": {
     "@babel/cli": "7.0.0-beta.52",
     "@babel/core": "7.0.0-beta.52",
-    "@babel/plugin-external-helpers": "7.0.0-beta.53",
+    "@babel/plugin-external-helpers": "7.0.0-beta.52",
     "@babel/preset-env": "7.0.0-beta.52",
     "@babel/preset-typescript": "7.0.0-beta.53",
     "babel-eslint": "8.2.5",

yarn.lock

@@ -281,11 +281,11 @@
   version "7.0.0-beta.52"
   resolved "https://registry.yarnpkg.com/@babel/parser/-/parser-7.0.0-beta.52.tgz#4e935b62cd9bf872bd37bcf1f63d82fe7b0237a2"
 
-"@babel/plugin-external-helpers@7.0.0-beta.53":
-  version "7.0.0-beta.53"
-  resolved "https://registry.yarnpkg.com/@babel/plugin-external-helpers/-/plugin-external-helpers-7.0.0-beta.53.tgz#58c308627e1c057377e1e871a6a27dd3808d2db7"
+"@babel/plugin-external-helpers@7.0.0-beta.52":
+  version "7.0.0-beta.52"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-external-helpers/-/plugin-external-helpers-7.0.0-beta.52.tgz#26e81700679faf26111a7ce1be5d8c774e6f2cf8"
   dependencies:
-    "@babel/helper-plugin-utils" "7.0.0-beta.53"
+    "@babel/helper-plugin-utils" "7.0.0-beta.52"
 
 "@babel/plugin-proposal-async-generator-functions@7.0.0-beta.52":
   version "7.0.0-beta.52"