chore(rds): add Aurora Postgres 16.2 cluster support (#30122)

### Issue # (if applicable)

N/A

### Reason for this change

Cluster can be upgraded/created to Postgres 16.2 via the console/CLI but not CDK.

### Description of changes

Adds support for Postgres 16.2 Aurora cluster, 16.2 instances are already supported.

### Description of how you validated changes

N/A

### 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*

packages/aws-cdk-lib/aws-rds/lib/cluster-engine.ts

@@ -975,6 +975,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_16_0 = AuroraPostgresEngineVersion.of('16.0', '16', { s3Import: true, s3Export: true });
   /** Version "16.1". */
   public static readonly VER_16_1 = AuroraPostgresEngineVersion.of('16.1', '16', { s3Import: true, s3Export: true });
+  /** Version "16.2". */
+  public static readonly VER_16_2 = AuroraPostgresEngineVersion.of('16.2', '16', { s3Import: true, s3Export: true });
 
   /**
    * Create a new AuroraPostgresEngineVersion with an arbitrary version.