[BUG] Discriminated set models contain same value on discriminator values in purview

[ArcturusZhang]

API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/1c7df99f6a84335cfd7bf5be8c800d72c1dddbc2/specification/purview/data-plane/Azure.Analytics.Purview.Scanning/preview/2018-12-01-preview/scanningService.json

API Spec version

2018-12-01-preview

Describe the bug

azure-rest-api-specs/specification/purview/data-plane/Azure.Analytics.Purview.Scanning/preview/2018-12-01-preview/scanningService.json

Lines 6368 to 6386 in 1c7df99

	"AzureSubscriptionSystemScanRuleset": {
	"type": "object",
	"allOf": [
	{
	"$ref": "#/definitions/SystemScanRuleset"
	}
	],
	"properties": {
	"properties": {
	"allOf": [
	{
	"$ref": "#/definitions/AzureSubscriptionScanRulesetProperties"
	}
	]
	}
	},
	"x-ms-discriminator-value": "None"
	},
	"AzureResourceGroupSystemScanRuleset": {

Here we have two models in the same discriminated set but they have the same discriminator value: None
This is incorrect.

Expected behavior

Every variant in a discriminated set should have unique discriminator values

Actual behavior

2 of them have the same value.

Reproduction Steps

Just check the swagger.

Environment

Irrelevant

[zzhxiaofeng]

@parvsaxena Please help have a look, thank you.