lock inquirer dependency, fixes vuejs#4177

This should revert the upstream bug identified here: SBoudrias/Inquirer.js#811

Author: slhck

package.json

@@ -60,7 +60,7 @@
     "globby": "^9.2.0",
     "graphql": "^14.3.1",
     "http-server": "^0.11.1",
-    "inquirer": "^6.3.1",
+    "inquirer": "~6.3.1",
     "jest": "^24.7.1",
     "lerna": "^3.13.4",
     "lerna-changelog": "^0.8.2",