Fix: Upcoming breaking changes in the cmdlet

[barrjam]

These are from Get-AzLandingZone, other commands produce similar warnings

Get-AzManagementGroup

WARNING: Upcoming breaking changes in the cmdlet 'Get-AzManagementGroup' :

- The parameter : 'GroupName' is being replaced by parameter : 'GroupId'.
- Change description : We will replace GroupName with GroupId to make it more clear. 
Note : Go to https://aka.ms/azps-changewarnings for steps to suppress this breaking change warning, and other information on breaking changes in Azure PowerShell.

Get-AzPolicyAssignment

WARNING: Upcoming breaking changes in the cmdlet 'Get-AzPolicyAssignment' :                                                                                                                                                                                                                                                                                                                                                       - The output type 'Microsoft.Azure.Commands.ResourceManager.Cmdlets.Implementation.Policy.PsPolicyAssignment' is changing                                                                                        - The following properties are being added to the output type : 'Identity'                                                                                                                                       
Note : Go to https://aka.ms/azps-changewarnings for steps to suppress this breaking change warning, and other information on breaking changes in Azure PowerShell.

Get-AzEventHubNamespace

WARNING: Upcoming breaking changes in the cmdlet 'Get-AzEventHubNamespace' :                                                                                                                                                                                                                                                                                                                                                      - The output type 'Microsoft.Azure.Commands.EventHub.Models.PSNamespaceAttributes' is changing                                                                                                                   - The following properties in the output type are being deprecated : 'ResourceGroup'                                                                                                                             
- The following properties are being added to the output type : 'ResourceGroupName' 'Tags'
Note : Go to https://aka.ms/azps-changewarnings for steps to suppress this breaking change warning, and other information on breaking changes in Azure PowerShell.