Link to local version of strapi-plugin-config-sync.

Linking to "boazpoolman/strapi-plugin-config-sync" resolves to the
version of strapi-plugin-config-sync currently on master branch on
GitHub. Which prevents running tests in the playground against the local
version.

Author: goodhoko

playground/package.json

@@ -19,7 +19,7 @@
     "@strapi/plugin-users-permissions": "^4.0.0",
     "@strapi/strapi": "^4.0.0",
     "sqlite3": "5.0.2",
-    "strapi-plugin-config-sync": "boazpoolman/strapi-plugin-config-sync"
+    "strapi-plugin-config-sync": "./.."
   },
   "author": {
     "name": "A Strapi developer"