Update Microsoft.Chaos API Version 2021-09-15-preview types/experiment.json (Azure#16480)

Author: mariohdez

specification/chaos/resource-manager/Microsoft.Chaos/preview/2021-09-15-preview/types/experiments.json

@@ -344,7 +344,7 @@
           "type": "string",
           "description": "Enum of the Target reference type.",
           "enum": [
-            "ResourceId"
+            "ChaosTarget"
           ],
           "x-ms-enum": {
             "name": "TargetReferenceType",