[ReleasePR purview] Updated SKU property to be read only (#1892)

Create to sync Azure/azure-rest-api-specs#15965
[ReCreate this PR](https://github.com/azure-resource-manager-schemas/compare/main...AzureSDKAutomation:sdkAuto/purview?expand=1)

Author: msftbot[bot]

schemas/2020-12-01-preview/Microsoft.Purview.json

@@ -53,17 +53,6 @@
             ]
           }
         },
-        "sku": {
-          "oneOf": [
-            {
-              "$ref": "#/definitions/AccountSku"
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "The Sku"
-        },
         "tags": {
           "oneOf": [
             {
@@ -171,37 +160,6 @@
       },
       "description": "The account properties"
     },
-    "AccountSku": {
-      "type": "object",
-      "properties": {
-        "capacity": {
-          "oneOf": [
-            {
-              "type": "integer"
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "Gets or sets the sku capacity. Possible values include: 4, 16"
-        },
-        "name": {
-          "oneOf": [
-            {
-              "type": "string",
-              "enum": [
-                "Standard"
-              ]
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "Gets or sets the sku name."
-        }
-      },
-      "description": "The Sku"
-    },
     "accounts_privateEndpointConnections_childResource": {
       "type": "object",
       "properties": {

schemas/2021-07-01/Microsoft.Purview.json

@@ -53,17 +53,6 @@
             ]
           }
         },
-        "sku": {
-          "oneOf": [
-            {
-              "$ref": "#/definitions/AccountSku"
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "The Sku"
-        },
         "tags": {
           "oneOf": [
             {
@@ -171,37 +160,6 @@
       },
       "description": "The account properties"
     },
-    "AccountSku": {
-      "type": "object",
-      "properties": {
-        "capacity": {
-          "oneOf": [
-            {
-              "type": "integer"
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "Gets or sets the sku capacity. Possible values include: 4, 16"
-        },
-        "name": {
-          "oneOf": [
-            {
-              "type": "string",
-              "enum": [
-                "Standard"
-              ]
-            },
-            {
-              "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
-            }
-          ],
-          "description": "Gets or sets the sku name."
-        }
-      },
-      "description": "The Sku"
-    },
     "accounts_privateEndpointConnections_childResource": {
       "type": "object",
       "properties": {