Remove delimiter from list blob flat segment response (#7376)

Resolves #7350

Author: jeremymeng

specification/storage/data-plane/Microsoft.BlobStorage/preview/2019-02-02/blob.json

@@ -8254,9 +8254,6 @@
         "MaxResults": {
           "type": "integer"
         },
-        "Delimiter": {
-          "type": "string"
-        },
         "Segment": {
           "$ref": "#/definitions/BlobFlatListSegment"
         },