TypeSpec rewrite clashes with legacy hand-written spec.

https://github.com/Azure/azure-rest-api-specs/blob/3f819f6fc843ddd081b700edeeb1e238443e4da6/specification/monitor/resource-manager/Microsoft.Insights/Insights/preview/2021-05-01-preview/diagnosticsSettings_API.json

duplicates part of `openapi.json` with differing content:

```json
"/{resourceUri}/providers/Microsoft.Insights/diagnosticSettingsCategories": {
"get": {
"description": "Lists the diagnostic settings categories for the specified resource.",
"operationId": "DiagnosticSettingsCategory_List",
"parameters": [
{
"$ref": "#/parameters/ResourceUriParameter"
},
{
"$ref": "../../../../../../common-types/resource-management/v2/types.json#/parameters/ApiVersionParameter"
}
],
"responses": {
"200": {
"description": "Successful request to get more information about diagnostic setting category",
"schema": {
"$ref": "#/definitions/DiagnosticSettingsCategoryResourceCollection"
}
},
"default": {
"description": "Error response describing why the operation failed.",
"schema": {
"$ref": "#/definitions/ErrorResponse"
}
}
},
"tags": [
"DiagnosticSettingsCategories"
],
"x-ms-examples": {
"Gets the diagnostic setting": {
"$ref": "./examples/listDiagnosticSettingsCategories.json"
}
},
"x-ms-pageable": {
"nextLinkName": null
}
}
},
```

vs

```json
"/{resourceUri}/providers/Microsoft.Insights/diagnosticSettingsCategories": {
"get": {
"description": "Lists the diagnostic settings categories for the specified resource.",
"operationId": "DiagnosticSettingsCategory_List",
"parameters": [
{
"$ref": "../../../../../../common-types/resource-management/v5/types.json#/parameters/ApiVersionParameter"
},
{
"description": "The fully qualified Azure Resource manager identifier of the resource.",
"in": "path",
"name": "resourceUri",
"required": true,
"type": "string",
"x-ms-skip-url-encoding": true
}
],
"responses": {
"200": {
"description": "Azure operation completed successfully.",
"schema": {
"$ref": "#/definitions/DiagnosticSettingsCategoryResourceCollection"
}
},
"default": {
"description": "An unexpected error response.",
"schema": {
"$ref": "#/definitions/Microsoft.Common.ErrorResponse"
}
}
},
"tags": [
"DiagnosticSettingsCategories"
],
"x-ms-examples": {
"Gets the diagnostic setting": {
"$ref": "./examples/listDiagnosticSettingsCategories.json"
}
},
"x-ms-pageable": {
"nextLinkName": "nextLink"
}
}
},
```

tl;dr `"nextLinkName": null` => `"nextLinkName": "nextLink"`

The legacy file should be removed?