Data type of some input parameter on doc is not friendly

### Description
The type of some input parameter on public doc is not friendly. For instance, the one of input type of Set-AzAutomationWebhook is below:
```
System.Nullable`1[[System.Boolean, System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]
```

### Expected Result
```
System.Nullable
```
Nullable and Boolean should link to struct description of .NET API doc (it won't be tracked by this issue because it is doc team's improvement)
https://docs.microsoft.com/en-us/dotnet/api/system.boolean
https://docs.microsoft.com/en-us/dotnet/api/system.nullable-1

Start with the public documentation for the Set-AzAutomationWebhook cmdlet and inspect how nullable .NET parameter types are rendered. Update the documentation output so the type uses the readable System.Nullable form, then verify that the Nullable and Boolean references link to the .NET API documentation.

Written by the indexing model from the issue text.