[SecurityInsight][bug] body parameter shall be `required`

When I call the following API without body: https://github.com/Azure/azure-rest-api-specs/blob/4d150f815b378ea4eb60128e0b0458210a46d2ab/specification/securityinsights/resource-manager/Microsoft.SecurityInsights/preview/2022-12-01-preview/OnboardingStates.json#L81-L111

I get the error:
```
(BadRequest) A non-empty request body is required.
```
But according to swagger definition, `SentinelOnboardingStateParameter` is not required:
https://github.com/Azure/azure-rest-api-specs/blob/4d150f815b378ea4eb60128e0b0458210a46d2ab/specification/securityinsights/resource-manager/Microsoft.SecurityInsights/preview/2022-12-01-preview/OnboardingStates.json#L273-L284

So I think the swagger definition is not right, it shall be:
```json
...
"required": true,
...
```

Open specification/securityinsights/resource-manager/Microsoft.SecurityInsights/preview/2022-12-01-preview/OnboardingStates.json and inspect the operation around lines 81-111 and SentinelOnboardingStateParameter around lines 273-284. Confirm the API requires a non-empty body, then update the parameter definition so its required setting matches that behavior.

Written by the indexing model from the issue text.