software/nextcloud: fix copy & pasted description in schema

software/erp5/instance-erp5-input-schema.json

 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "description": "Parameters to instantiate ERP5",
+  "type": "object",
   "additionalProperties": false,
   "definitions": {
     "routing-rule-list": {

software/jstestnode/instance-jstestnode-input-schema.json

 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "description": "Parameters to instantiate JSTestNode",
+  "type": "object",
   "additionalProperties": false,
   "required": [
     "test-suite",

software/nextcloud/nextcloud-input-schema.json

 {
   "$schema": "http://json-schema.org/draft-04/schema#",
-  "description": "Parameters to instantiate Grafana",
+  "description": "Parameters to instantiate NextCloud",
+  "type": "object",
   "additionalProperties": false,
   "properties": {
     "domain": {