(apigateway): RestApi not redeploying correctly

When I change a resource path in a RestApi the old path is not removed from the api stage.
The `deploy` option of RestApi should update the stage when a change occur in the api.

### Reproduction Steps
The initial stack:

const api: RestApi = new RestApi(this, 'rest-api', {
deploy: true,
deployOptions: {
stageName: 'test-stage'
}
})

const myResource:IResource = api.root.addResource("myResource", {})

myResource.addMethod("GET",
new Integration({
type:IntegrationType.MOCK,
integrationHttpMethod:'ANY'
})
)

The deployed resources:
The stage:

If I change the path of the resource:
`const myResource:IResource = api.root.addResource("myResourceChanged", {})
`
and redeploy the stack

### What did you expect to happen?
The expect deployed resources:
The expect stage:

### What actually happened?
The new deployed resources:
The new stage:

If I manually redeploy the stage from the console, the /myResource is removed from the stage.

### Environment

- **CDK CLI Version :*1.103.0 (build bc13a66)*
- **Framework Version:**
- **Node.js Version:*v14.13.1*
- **OS :*Windows 10*
- **Language (Version):*TypeScript(3.9.7)*

### Other

---

This is :bug: Bug Report

Start by reproducing the TypeScript RestApi example with deploy enabled and a named stage, then inspect the RestApi deployment behavior when the resource path changes. Done means redeploying the stack removes the old path from the API stage without requiring a manual console redeployment.

Written by the indexing model from the issue text.