chore(rds): postgres 16.13 (#37540)

### Issue # (if applicable)

None

### Reason for this change

https://docs.aws.amazon.com/AmazonRDS/latest/PostgreSQLReleaseNotes/postgresql-versions.html#postgresql-versions-version1613

### Description of changes

### Describe any new or updated permissions being added

### Description of how you validated changes

```
aws rds describe-db-engine-versions --engine aurora-postgresql --output table --query 'DBEngineVersions[*].{Engine:Engine,EngineVersion:EngineVersion}'

------------------------------------------
|        DescribeDBEngineVersions        |
+--------------------+-------------------+
|       Engine       |   EngineVersion   |
+--------------------+-------------------+
...
|  aurora-postgresql |  16.11            |
|  aurora-postgresql |  16.11-limitless  |
|  aurora-postgresql |  16.13            |
...
```

### 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: phadadi

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

@@ -1372,6 +1372,8 @@ export class AuroraPostgresEngineVersion {
   public static readonly VER_16_11 = AuroraPostgresEngineVersion.of('16.11', '16', { s3Import: true, s3Export: true });
   /** Version "16.11 limitless". */
   public static readonly VER_16_11_LIMITLESS = AuroraPostgresEngineVersion.of('16.11-limitless', '16', { s3Import: true, s3Export: true });
+  /** Version "16.13". */
+  public static readonly VER_16_13 = AuroraPostgresEngineVersion.of('16.13', '16', { s3Import: true, s3Export: true });
 
   /**
    * Version "17.1"