fix(ec2): update RouterType.GATEWAY JSDoc to mention Virtual Private Gateway

[deveshsinghal09]

Issue # (if applicable)

Closes #37632

Summary

Fixes the misleading JSDoc comment on RouterType.GATEWAY in aws-ec2.

Problem

The doc comment on RouterType.GATEWAY only mentioned Internet Gateway, but the underlying CloudFormation GatewayId property actually accepts both an Internet Gateway ID and a Virtual Private Gateway ID:

The ID of an internet gateway or virtual private gateway attached to your VPC.

This makes the API misleading for users who want to add a route targeting a Virtual Private Gateway (VGW), as shown in the issue.

Solution

Updated the JSDoc comment to accurately reflect both supported gateway types and added a @see link to the CloudFormation reference documentation.

Changes

• packages/aws-cdk-lib/aws-ec2/lib/vpc.ts: Updated RouterType.GATEWAY JSDoc comment

Additional Notes

• This is a documentation-only change — no behavior or API changes, zero breaking change risk.
• The existing tests at vpc.test.ts already cover RouterType.GATEWAY usage; no new tests needed for a comment fix.

[aws-cdk-automation]

The pull request linter fails with the following errors:

❌ Fixes must contain a change to a test file.
❌ Fixes must contain a change to an integration test file and the resulting snapshot.

If you believe this pull request should receive an exemption, please comment and provide a justification. A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed, add Clarification Request to a comment.

✅ A exemption request has been requested. Please wait for a maintainer's review.

[deveshsinghal09]

Exemption Request: This PR only updates a JSDoc comment for the RouterType.GATEWAY enum to improve documentation. There are no functional code changes that require unit or integration tests.

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