chore(rds): added Postgres 16.7 version (#33509)

### Issue # (if applicable)

Closes #33508.

### Reason for this change
Per [Amazon RDS for PostgreSQL updates](https://docs.aws.amazon.com/AmazonRDS/latest/PostgreSQLReleaseNotes/postgresql-versions.html), PostgreSQL version `16.7` is now available on Amazon RDS.

Executing AWS CLI command `aws rds describe-db-engine-versions --engine postgres --output table --query 'DBEngineVersions[*].{Engine:Engine,EngineVersion:EngineVersion}'` also lists `16.7` as one of the supported versions.

### Description of changes
Added `16.7` version to `PostgresEngineVersion` class.

### Describe any new or updated permissions being added




### Description of how you validated changes



### Checklist
- [ ] 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: ashishdhingra

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

@@ -1732,6 +1732,8 @@ export class PostgresEngineVersion {
   public static readonly VER_16_5 = PostgresEngineVersion.of('16.5', '16', { s3Import: true, s3Export: true });
   /** Version "16.6" */
   public static readonly VER_16_6 = PostgresEngineVersion.of('16.6', '16', { s3Import: true, s3Export: true });
+  /** Version "16.7" */
+  public static readonly VER_16_7 = PostgresEngineVersion.of('16.7', '16', { s3Import: true, s3Export: true });
 
   /** Version "17" (only a major version, without a specific minor version). */
   public static readonly VER_17 = PostgresEngineVersion.of('17', '17', { s3Import: true, s3Export: true });