Remove Az.App and Az.Portal installation from Github Action

[msha1026]

As an engineer, I would like to remove Az.App and Az.Portal installation from our various Github workflows and documentation, so that it is no longer an additional step after installing Az module.

Az.App and Az.Portal are still not "GA" yet, so it is not a dependency on the main Az PowerShell module. As a result, Az.App and Az.Portal are not installed as a part of Az. This problem was resolved in this PR #286. However, when Az.App and Az.Portal are "GA" aka their versions have been bumped to 1.0.0, Az.App and Az.Portal will become dependencies on the main Az PowerShell module. That would mean, we do not need to have an extra step to specifically install Az.App and Az.Portal anymore. When this happens, the Az.App and Az.Portal installations that happened in PR #286 will need to be reverted.

• Az.App installation and documentation changes that were made in PR Container Application Support #286 are reverted
• Az.Portal installation and documentation changes that were made in PR TBD are reverted

[msha1026]

Az.Portal installation will also need to be removed from Github actions for the same reasons. Additional information: Azure/azure-powershell#21363. Adding it as acceptance criteria.