Deprecated Amazon Chime SDK API on the "chime" endpoint

### **Describe the bug**
The **televisit-demo backend** app uses a deprecated API endpoint, which makes to fail the CFN stack deployment.

### **To Reproduce**
Steps to reproduce the behavior:
Run deployment script form amazon-chime-sdk/apps/televisit-demo/backend
The **chime-sdk-televisit-backend** CFN stack creating will fail with the error message:

> CloudFormation did not receive a response from your Custom Resource.

The custom resource should invoke the ChimeAppInstanceLambda Function. However the Lambda function fails with the following error:

> Account Id xxxx is not authorized to call deprecated Amazon Chime SDK API on the "chime" endpoint, use one of the "*-chime*" endpoints instead.

### **Expected behavior**
The code should use the appropriate API endpoint, as described in:
https://docs.aws.amazon.com/chime-sdk/latest/APIReference/API_voice-chime_AssociatePhoneNumbersWithVoiceConnector.html

### **Additional context**
The same exact bug has been fixed in https://github.com/cdklabs/cdk-amazon-chime-resources/issues/501

Start with the deployment script under amazon-chime-sdk/apps/televisit-demo/backend and trace the custom resource that invokes the ChimeAppInstanceLambda Function. Compare its endpoint with the linked Amazon Chime SDK API documentation and the related fix in cdklabs/cdk-amazon-chime-resources issue 501; done means the CFN stack deploys without the deprecated-endpoint error.

Written by the indexing model from the issue text.