Update documentation when on-behalf-of flow is supported by azure identity

currently OBO is not supported by azure-identity. There are plans to add support for it.
Whenever support is added [this page](https://docs.microsoft.com/en-us/graph/sdks/choose-authentication-providers?tabs=Java) needs to be updated 
[AB#7986](https://microsoftgraph.visualstudio.com/0985d294-5762-4bc2-a565-161ef349ca3e/_workitems/edit/7986)