Remove default user and password from default.json

This commit removes the user and password from `config/default.json`.
This allows to not set a username and password when connecting to
Elasticsearch; Previously the default values were used if username and
password were omitted from `config/local.json`

Fixes #358
Signed-off-by: Kevin Gimbel <hallo@kevingimbel.com>

Author: KevinGimbel

config/default.json

@@ -14,8 +14,6 @@
     "host": "localhost",
     "port": 9200,
     "protocol": "http",
-    "user": "elastic",
-    "password": "changeme",
     "min_score": 0.01,
     "indices": [
       "vue_storefront_catalog",