[BUG] Subscription override warning message (ephemeral storage)

## To Reproduce

1. Follow the steps in https://learn.microsoft.com/en-us/azure/cloud-shell/get-started/ephemeral?tabs=powershell
2. Use the command in the supplied warning message (`Update-AzConfig -DefaultSubscriptionForLogin`) to set the default subscription to the desired subscription
3. Restart the shell

## Observed Behavior

```
Requesting a Cloud Shell.Succeeded.
Connecting terminal...

Your Cloud Shell session will be ephemeral so no files or system changes will persist beyond your current session.

MOTD: SqlServer has been updated to Version 22!

VERBOSE: Authenticating to Azure ...
WARNING: TenantId '{my tenant id}' contains more than one active subscription. First one will be selected for further use. To select another subscription, use Set-AzContext.
WARNING: To override which subscription Connect-AzAccount selects by default, use `Update-AzConfig -DefaultSubscriptionForLogin 00000000-0000-0000-0000-000000000000`. Go to https://go.microsoft.com/fwlink/?linkid=2200610 for more information.
VERBOSE: Building your Azure drive ...
```

## Expected behavior

Ideally, I would love the default subscription configuration to persist through the ephemeral session.

That being said, I understand that there are limitations to the ephemeral cloud shell. If the setting cannot be persisted, the override warning should be suppressed as to not misdirect ephemeral cloud shell users. (That warning and the message about "no files or system changes" appear to be at odds)

## Is this specific to Cloud Shell?
Not sure how to answer this question, since it seems to be an edge case interaction between Azure Powershell and Azure Cloud Shell. I don't believe that this issue would make sense in the Azure Powershell repo (as it is a specific quirk of the ephemeral implementation of Azure Cloud Shell).

## Interface information
How are you accessing Cloud Shell - portal.azure.com
If a browser, which Operating System and browser are you using? Firefox on Windows 11

## Additional context
I know this is maybe a minor gripe, but it's definitely confusing, especially as a new user, to be prompted with a warning whose instructions do not resolve the issue.

I have no issue with the first warning message (re: multiple subscriptions), and I definitely think that the first warning is important to have regardless of whether this issue is resolved by suppressing the second warning or incorporating some way to persist the default subscription selection.

Beginnen Sie mit dem Cloud Shell-Startup-Ablauf, der sich bei Azure authentifiziert und die Abonnementwarnungen ausgibt, und reproduzieren Sie anschließend das Verhalten der flüchtigen Sitzung mit dem dokumentierten Befehl Update-AzConfig. Als erledigt gilt die Aufgabe, wenn entweder das Standardabonnement für die Sitzung bestehen bleibt oder die Überschreibungswarnung unterdrückt wird, wenn die Persistenz nicht verfügbar ist, ohne die Warnung zu mehreren Abonnements zu entfernen.

Vom Indexierungsmodell aus dem Issue-Text verfasst.