docs(ecs): make correction to documentation for windows containers network mode support (#35007)

### Issue # (if applicable)

Closes #35006.

### Reason for this change

The documentation for NetworkMode.NAT enum incorrectly states that NAT is "the only supported network mode for Windows containers". This is no longer accurate as Windows containers also support the `awsvpc` network mode according to AWS documentation. 

### Description of changes

- Removed the incorrect sentence stating "This is the only supported network mode for Windows containers."
- Updated the description of NAT mode to clarify that it's "Docker's built-in virtual network which runs inside each Windows container instance" without implying exclusivity.

### Describe any new or updated permissions being added

None. This change is documentation-only and doesn't modify any code logic or permissions.

### Description of how you validated changes

None

### Checklist
- [X] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: evzzk

packages/aws-cdk-lib/aws-ecs/lib/base/task-definition.ts

@@ -971,10 +971,7 @@ export enum NetworkMode {
   HOST = 'host',
 
   /**
-   * The task utilizes NAT network mode required by Windows containers.
-   *
-   * This is the only supported network mode for Windows containers. For more information, see
-   * [Task Definition Parameters](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#network_mode).
+   * The task utilizes Docker's built-in virtual network which runs inside each Windows container instance.
    */
   NAT = 'nat',
 }