Copilot Chat: Disable alwaysOn and enable health check (#2084)

### Motivation and Context

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Addressing item
https://github.com/microsoft/semantic-kernel/issues/1702.

### Description
Instead of mapping / to /healthz, we decided to disable alwaysOn and
enable App Service health check. This is because mapping / to /healthz
creates a dependency on the deployment setup and makes the code harder
to maintain, i.e when alwaysOn is disabled, there is really not point at
mapping the route. Thus, disabling alwaysOn and enabling App service
health check is a cleaner solution.

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### Contribution Checklist

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#dev-scripts)
raises no violations
- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

samples/apps/copilot-chat-app/deploy/main.bicep

@@ -134,14 +134,17 @@ resource appServiceWeb 'Microsoft.Web/sites@2022-09-01' = {
     serverFarmId: appServicePlan.id
     httpsOnly: true
     virtualNetworkSubnetId: virtualNetwork.properties.subnets[0].id
+    siteConfig: {
+      healthCheckPath: '/healthz'
+    }
   }
 }
 
 resource appServiceWebConfig 'Microsoft.Web/sites/config@2022-09-01' = {
   parent: appServiceWeb
   name: 'web'
   properties: {
-    alwaysOn: true
+    alwaysOn: false
     cors: {
       allowedOrigins: [
         'http://localhost:3000'