Drop URL validation on ElasticSearch for apiUmbrella form

For OpenShift/Kubernetes (or cloud services) Elasticsearch can be available by host name and the previously regex doesn't allow adding just 'http://elasticsearch'

proxies/collection/schemas/api_umbrella.js

@@ -23,6 +23,5 @@ export default {
   },
   'apiUmbrella.elasticsearch': {
     type: String,
-    regEx: SimpleSchema.RegEx.Url,
   },
 };