[Microsoft.Network/vpnGateways]: Inaccurate read-only on natRules/properties/egressVpnSiteLinkConnections

### Resource Type

Microsoft.Network/vpnGateways

### Api Version

2023-06-01

### Issue Type

Property(s) inaccurately marked read-only/write-only

### Other Notes

According to documentation, there is no way to associate an VpnSite with a nat rule on the VPN Gateway using Bicep. This is faulty documentation for ARM, Bicep.

### Bicep Repro
```
resource vpngateway 'Microsoft.Network/vpnGateways@2023-06-01' = {
name: vpnGatewayName
. . .
properties: {
. . .
natRules : [
{
. . .
properties:{
. . .
egressVpnSiteLinkConnections: [
{
id:
}
]
}
}
]
}
}
```
### Confirm

- [X] I have read the troubleshooting guide and looked for duplicates.

Locate the Microsoft.Network/vpnGateways type definition for API version 2023-06-01 and inspect the metadata for natRules/properties/egressVpnSiteLinkConnections. Done means the definition accurately permits the VpnSite link association shown in the Bicep reproduction.

Written by the indexing model from the issue text.