@aws-cdk/aws-cloudfront.experimental: incorrect documentation on role parameter

### Describe the bug

Lambda@Edge functions does not return the role object when using `cloudfront.experimental.EdgeFunction` construct.

### Expected Behavior

`EdgeFunction.role` should return an `iam.Role`/`iam.IRole` object.

### Current Behavior

`EdgeFunction.role` returns `undefined`

### Reproduction Steps

### 1. Initiate a typescript project.
> `mkdir cdk-project && cd cdk-project && cdk init --language typescript`
### 2. Add required dependencies to the project.
> `import * as cloudfront from "aws-cdk-lib/aws-cloudfront";`
### 3. Create an `EdgeFunction` resource.
> `const func = new cloudfront.experimental.EdgeFunction(this, "LambdaAtEdge", {...lambdaProps});`

### Possible Solution

### `role` property on the [EdgeFunction](https://github.com/aws/aws-cdk/blob/ab7668197b1d7d7d08654d49df0c5ad9cb61b960/packages/%40aws-cdk/aws-cloudfront/lib/experimental/edge-function.ts#L48) must be initialized.
- The `role` property has been declared, but not initialized on the constructor.

### Additional Information/Context

_No response_

### CDK CLI Version

2.40.0

### Framework Version

_No response_

### Node.js Version

18.3

### OS

Windows 10 Version: 21H2 Build: 19044

### Language

Typescript

### Language Version

3.9.7

### Other information

_No response_

The referenced implementation is packages/@aws-cdk/aws-cloudfront/lib/experimental/edge-function.ts, where the EdgeFunction role property is declared. Start by inspecting that constructor and reproducing the TypeScript example; done means EdgeFunction.role returns an iam.Role/iam.IRole object instead of undefined.

Written by the indexing model from the issue text.