GraphRbac needs update

As per [application update](https://docs.microsoft.com/en-us/graph/api/application-update?view=graph-rest-1.0&tabs=http) and [service principal](https://docs.microsoft.com/en-us/graph/api/serviceprincipal-update?view=graph-rest-1.0&tabs=http),
```
Using PATCH to set passwordCredential is not supported. Use the addPassword and removePassword methods to update the password for a servicePrincipal.
```
The new APIs should be updated in GraphRbac.

Start with the GraphRbac API definitions and compare the application update and service principal update documentation linked in the issue. Done means the specification reflects addPassword and removePassword for password updates instead of relying on PATCH passwordCredential.

Written by the indexing model from the issue text.