Corect duplicate parent references in timeseriesinsights@2018-08-15-preview (#19010)

* Corect duplicate parent references in timeseriesinsights@2018-08-15-preview

* Remove invalid x-ms-discriminator-value extensions

Author: jeskew

specification/timeseriesinsights/resource-manager/Microsoft.TimeSeriesInsights/preview/2018-08-15-preview/timeseriesinsights.json

@@ -1612,9 +1612,6 @@
         },
         {
           "$ref": "#/definitions/EnvironmentResourceProperties"
-        },
-        {
-          "$ref": "#/definitions/ResourceProperties"
         }
       ],
       "required": [
@@ -1648,9 +1645,6 @@
       "allOf": [
         {
           "$ref": "#/definitions/EnvironmentResourceProperties"
-        },
-        {
-          "$ref": "#/definitions/ResourceProperties"
         }
       ],
       "description": "Properties of the long-term environment."
@@ -1908,7 +1902,6 @@
     },
     "EventHubEventSourceUpdateParameters": {
       "type": "object",
-      "x-ms-discriminator-value": "Microsoft.EventHub",
       "properties": {
         "properties": {
           "x-ms-client-flatten": true,
@@ -1924,7 +1917,6 @@
       "description": "Parameters supplied to the Update Event Source operation to update an EventHub event source."
     },
     "IoTHubEventSourceUpdateParameters": {
-      "x-ms-discriminator-value": "Microsoft.IoTHub",
       "type": "object",
       "properties": {
         "properties": {