`Microsoft.Web/sites` - `location` property not in type definition

Referencing https://github.com/Azure/bicep/issues/4815, `location` doesn't seem to be in the type definition for `Microsoft.Web/sites`. When trying to create a resource using the location of an existing site, I get the following error:

`This expression is being used in an assignment to the "location" property of the "Microsoft.Web/sites" type, which requires a value that can be calculated at the start of the deployment. Properties of webApp which can be calculated at the start include "apiVersion", "id", "name", "type".bicep(BCP120)`

For reference, below is the Bicep template. The input for the `location` property for webApp2 is what is throwing the error.

```yaml
param webAppName string = uniqueString(resourceGroup().id) // Generate unique String for web app name
param sku string = 'P1V2' // The SKU of App Service Plan
param location string = resourceGroup().location // Location for all resources

var appServicePlanName = toLower('mytestASP-${webAppName}')
var webSiteName = toLower('mytestwebappp-${webAppName}')

resource appServicePlan 'Microsoft.Web/serverfarms@2021-01-01' = {
name: appServicePlanName
location: location
properties: {
reserved: true
}
sku: {
name: sku
}
}

resource webApp 'Microsoft.Web/sites@2021-01-01' existing = {
name: 'testapp'
}

resource webApp2 'Microsoft.Web/sites@2021-01-01' = {
name: webSiteName
location: webApp.location
properties: {
serverFarmId: appServicePlan.id
}
}
```

Start with the Microsoft.Web/sites@2021-01-01 definition referenced by the template and compare it with the linked Azure Bicep issue #4815. Confirm how location is represented in this repository's specification data, then validate that an existing-site reference exposes it without BCP120.

Written by the indexing model from the issue text.