Not at all clear documentation.

## Description of the new feature
Transferring this [issue#1877](https://github.com/MicrosoftDocs/azure-docs-powershell/issues/1877) from **azure-docs-powershell** to **azure-powershell** repo.

FYI @dcaro and @Raag007

## Proposed implementation details (optional)

----------------------
**Document Details**

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

- ID: 2b963d11-ab7f-b257-2ec2-89e1327f1b0a
- Version Independent ID: dc1846a2-4d0a-fd2b-ecd1-1670435e86b6
- Content: Set-AzNetworkSecurityRuleConfig (Az.Network)
- Content Source: src/Network/Network/help/Set-AzNetworkSecurityRuleConfig.md
- Service: virtual-network
- GitHub Login: @dcaro
- Microsoft Alias: dcaro

Description: https://github.com/MicrosoftDocs/azure-docs-powershell/issues/1877#issuecomment-913783460
On your sandbox, when you get a chance please try to run these commands provided in this document.
```
$nsg = Get-AzNetworkSecurityGroup -Name "NSG-FrontEnd" -ResourceGroupName "TestRG"
$nsg | Get-AzNetworkSecurityRuleConfig -Name "rdp-rule"
Set-AzNetworkSecurityRuleConfig -Name "rdp-rule" -NetworkSecurityGroup $nsg -Access "Deny"
```

Start with src/Network/Network/help/Set-AzNetworkSecurityRuleConfig.md and review the linked source issue and its comment. Run the three provided PowerShell commands in a sandbox, then compare their behavior with the document. Done means the command sequence has been validated and any needed documentation correction is identified.

Written by the indexing model from the issue text.