fix($cli): bump CAC version (#1062)

Since --no-cache is defined, --cache/--no-cache can only be a boolean, and so any argument that you attempt to pass to --cache is interpreted as an individual argument, and in this case becomes the targetDir.

Author: spiltcoffee

packages/@vuepress/cli/package.json

@@ -28,7 +28,7 @@
     "url": "https://github.com/vuejs/vuepress/issues"
   },
   "dependencies": {
-    "cac": "^6.3.3",
+    "cac": "^6.3.6",
     "chalk": "^2.3.2",
     "semver": "^5.5.0"
   },

yarn.lock

@@ -1681,9 +1681,9 @@ byline@^5.0.0:
   version "5.0.0"
   resolved "https://registry.yarnpkg.com/byline/-/byline-5.0.0.tgz#741c5216468eadc457b03410118ad77de8c1ddb1"
 
-cac@^6.3.3:
-  version "6.3.3"
-  resolved "https://registry.yarnpkg.com/cac/-/cac-6.3.3.tgz#01e56f50068bd1be326b1612950d77d31112400d"
+cac@^6.3.6:
+  version "6.3.9"
+  resolved "https://registry.yarnpkg.com/cac/-/cac-6.3.9.tgz#0cdf3f2d3a7d3fb71ab89c476c73e472084859a2"
 
 cacache@^10.0.4:
   version "10.0.4"